Josh Marshall agrees that Weiner's resignation is without precedent:

What stands out to me about all this aren't Weiner's juvenile and mortifying 'offenses,' but the bizarre and almost inexplicable and unprecedented calls for his resignation. I don't think anyone will disagree with me that the open and insistent demands for his resignation from the Minority Leader, the Chairman of his party, the head of the House campaign committee and everyone else is simply unprecedented.

David Kurtz thinks part of the reason Weiner had to go was because he was "a proxy for the [Democratic party] leadership." Jonathan Bernstein blames the lying:

Weiner’s colleagues turned on him almost certainly because he lied, and because of how he lied — because of the very specific lie that he told. If Weiner had ‘fessed up from the beginning, I suspect he would have survived.

Joyner asks relevant questions:

Is Weiner’s scandal really worse than that of those who survived? How much of his Democratic colleagues’ reaction against him is personal? And how much of it is sheer electoral politics, given that he’s in a safe Democratic territory and New York will be losing seats in the next Congress, anyway?

Ezra Klein claims that Weiner is "paying for how media-friendly his indiscretions were."