Serious, yes, if perhaps becoming more common in Congressional testimony.  Rep. Justin Amash (R-MI)  posted a demand on his Facebook page for the resignation of James Clapper, Director of National Intelligence, after leaks showed that Clapper misled Congress in March about the activities of the NSA:

Libertarian Congressman Justin Amash (R-MI) called on Director of National Intelligence James Clapper to resign on Wednesday after a week of revelations surrounding the National Security Agency’s widespread surveillance of Americans.

“It now appears clear that the director of national intelligence, James Clapper, lied under oath to Congress and the American people,” Amash wrote on his Facebook. “Members of Congress can’t make informed decisions on intelligence issues when the head of the intelligence community willfully makes false statements. Perjury is a serious crime. Mr. Clapper should resign immediately.”

Amash took to Twitter as well:

Members of Congress can't make informed decisions on intelligence issues when head of intel community willfully makes false statements.

— Justin Amash (@justinamash) June 12, 2013

https://twitter.com/repjustinamash/status/344832065549778945

Perjury is a serious crime. Mr. Clapper should resign immediately.

— Justin Amash (@justinamash) June 12, 2013

If Mr. Clapper was concerned about revealing classified info, appropriate & lawful response is "That's classified" or "I can't answer that."

— Justin Amash (@justinamash) June 12, 2013

Clapper tried defending himself over the weekend, but ended up relying on a heavy parsing of the word “collection.”  Washington Post fact-checker Glenn Kessler gave Clapper three Pinocchios for the attempt:

In an interview with NBC’s Andrea Mitchell, he said that “I responded in what I thought was the most truthful, or least untruthful manner, by saying no,” though he also called his answer “too cute by half.” He indicated that his response to Wyden turned on a definition of “collect:” “There are honest differences on the semantics of what — when someone says ‘collection’ to me, that has a specific meaning, which may have a different meaning to him.”

One wonders why Clapper or his staff did not seek a clarification, given the apparent heads up by Wyden. Clapper apparently thinks the NSA “collects” only on specific targets — what he called, in the interview with NBC, “taking the book off the shelf and opening it up and reading it.” But that is a rather slippery answer.

In an interview with the National Journal, Clapper said: “What I said was, the NSA does not voyeuristically pore through U.S. citizens’ e-mails. I stand by that.” But neither Clapper nor Wyden referred to e-mails during the exchange. Wyden in fact referred to “any type of data at all” — which presumably would also cover the phone records in the other classified program that has been the subject of media reports. …

Given the information already in the public domain, including about e-mails, it is unclear what Clapper thought he was protecting with his “too cute by half” and “least untruthful” answer. Such important questions — and answers — should not be left to a semantic debate over the meaning of “collection.”

Clapper in recent days has tried to emphasize how forthright the NSA has been in explaining these programs. But he might have saved himself some trouble if he had been more forthright in the first place.

At Volokh Conspiracy, Jonathan Adler is also unimpressed with the defense:

It’s hard to argue that the NSA has not been engaged in the “collection” of information. If members of Congress are looking for an Administration official who gave untruthful testimony, it sees to me Clapper is a better candidate than Eric Holder. There is an added wrinkle here, however, is that it is not clear to me whether Clapper could have given a direct (and truthful) answer in a public hearing, as such an answer would have required him to disclose the existence of a then-classified government program. Even a non-answer or evasion could have revealed the existence of operations the NSA was trying to keep secret. In such a situation I would think one response would be to correct the record with the committee after-the-fact. Yet according to Senator Wyden’s office, no such correction was forthcoming — even after the Senator’s office gave him an opportunity to amend his answer. Admittedly Clapper was in a difficult situation, but it’s nonetheless clear that he was not truthful to Congress.

At 2 pm ET today, NSA Director Keith Alexander will testify at a Senate Appropriations Committee hearing, the first open testimony from anyone in this scandal since it broke.  Alexander arguably lied to Congress about the same thing in 2012, and this will be the first opportunity for either chamber to challenge the national-security team on their misleading public testimony:

As pressure mounts for the intelligence community to curb its surveillance activities or at least make them more transparent, a key National Security Agency official will testify before the Senate Appropriations Committee on Wednesday.

Army Gen. Keith Alexander, National Security Agency director and head of U.S. Cyber Command, will testify before the full committee in a previously-scheduled session, marking the first time an NSA official will answer to Congress in public since news broke that the agency is collecting all of Verizon’s U.S. phone records, as well as internet content from non-U.S. internet users abroad.

His predecessor, Michael Hayden, tried to back up Alexander in an interview with Eli Lake at the Daily Beast:

“Not all analysts have the power to target anything,” Snowden told The Guardian in an interview posted Sunday. “But I, sitting at my desk, had the authority to wiretap anyone, from you or your accountant to a federal judge to even the president if I had a personal email.”

Michael Hayden, a former NSA director and CIA director, said Snowden’s assertion was “absolutely outrageous.” “He was not a collector,” he said. “I don’t know he could do anything like that,” adding that Snowden, a low-ranking contractor, would not have the authority or access to listen in on phone calls or read emails from anyone. …

“Rogue collection” at the NSA over the years was extremely rare, the former top official said. Asked for an example, Hayden said he remembered a collector who was fired for trying to snoop on his ex-wife overseas.

“A rogue collector would lose his clearance and be run out of the organization,” said Joel Brenner, a former inspector general and senior counsel for the NSA who left the agency in 2010. Brenner said that he didn’t recall ever dealing with “rogue collecting” during his time at as inspector general.

In yesterday’s briefing, though, the FBI and NSA told Congress that they’re collecting a billion records a day — but just not searching through it without cause and court orders.  Even on the parsing, Clapper still seems to be misleading as to the nature of the program.  Perhaps Alexander will be more forthcoming this afternoon.