There's a lot of noise today about this particular item.
I see two particular points of interest.
One, the investigation highlights just how much intelligence-gathering the NSA was doing within the US, and how much of it was truly targeted at US citizens. Had this merely been about foreign agents plotting harm to the US as the programme was originally presented, Rep. Harman would have gone essentially unnoticed. However, she was not, and only the intervention of (then) Attorney General Gonzalez prevented a full-blown and very embarrassing investigation. Of course, now that the deal that was struck has been exposed, the embarrassment is compounded, so any benefit Harman received was strictly temporary.
Two, it showcases how widespread foreign involvement in US policymaking could potentially be, and how diverse the prospective "foreign agents" would be by inference. If Harman, then a House Intelligence Committee member, was amenable to quid pro quo with foreign agents despite (or perhaps because of) her responsibilities, the AIPAC moment might be only one of many. Also, if AIPAC was the foreign agency snared by the wiretap, it certainly makes wiretapping to "catch foreign terrorists" harder to justify unless one is willing to label Israel a state sponsor of terrorism, which the Conservatists are loath to do and which even the US Left is hesitant to consider. And Gonzalez' intervention says much about what the Bush maladministration was prepared to overlook to achieve its aims.
Harmon's subsequent distancing from authority by House leadership is certainly appropriate. Unless charges are preferred, though, her continuing in office is best left between her and her constituents for the moment.
UPDATE: Re. Harman has issued an not-quite-rebuttal statement to the charges. It seems she's missing the larger point, though the point she does make is certainly troubling.