Either you are with the Constitution, or you are with the terrorists.

So, I think Bush authorizing warrantless wire-tapping should be grounds for impeachment.

I'm not particularly angry about this particular incident, and I doubt it'd even make the top ten worst things he's done in office, but it seems particularly contrary to his duties as President.

When you're sworn into office, you say, "I do solemnly swear (or affirm) that I will faithfully execute the Office of President of the United States, and will to the best of my ability, preserve, protect, and defend the Constitution of the United States."

If the President, without the approval of Congress, willfully violates the Constitution (in this case, the Fourth Amendment), he's violating that oath.

The legal grounds for impeachment are extremely vague. The president (or anyone else in the Executive Branch) can only be impeached for committing, "treason, bribery, or other high crimes and misdemeanors." What constitutes a "high crime" is up to Congress to decide on a case-by-case basis.

Bill Clinton was impeached because Congress decided that getting a blow job and then lying about it was a high crime, which seems dubious, but for the sake of argument let's assume that's legitimate.
If lying about having sex is a high crime, isn't lying about upholding the constitution as well?*

I doubt it would happen, but it should. I'm not even saying he should be thrown out of office (though I certainly wouldn't shed any tears if he were), just that if he's going to take an action like that he should be prepared to deal with serious consequences.
It's possible that his actions were justified. But if that's the case, that should be determined by the people (well, Congress) not by him and his buddies.

According to Wikipedia, News of tapping sparked an outcry from many groups, including members of Congress, who feel such actions are a violation of constitutional rights. Senator Arlen Specter (R-PA), the chairman of the Senate Judiciary Committee, said that "there is no doubt this is inappropriate" and "clearly and categorically wrong" and that he would hold hearings into the matter early in 2006.

I'd like to think that those "hearings" would be something on this scale, though it does seem unlikely. Pissed though they may be, it's hard for to imagine that the Republican Party would be sufficiently indignant to throw Bush to the wolves.

But, as we say here in the biz, only time will tell.

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*No, he didn't lie about what he did. But he said he'd never do it, then did, then obscured that fact.