While the tuition fee thing didn't help, many of the Lib Dems MPs voted out on Thursday kept their promise to vote against. If elections are meant to be based far more on the person standing rather than the party they represent, to see some of them voted out was somewhat unfair. They kept their promise but were judged equally culpable by association apparently. Meanwhile, the chief culprit made it into parliament anyway. Not that Nick Clegg lasted much longer.
The Lib Dem's role in government has probably been quite useful, actually -- although I guess that depends on your personal politics. But their biggest policy point, lifting the minimum tax threshold by several thousand pounds in the end, was certainly a fine achievement and not at all something the Tories were going to do themselves. But they reaped what they have sowed, and while joining the Tory coalition was probably the right thing to do (certainly it's easier to buy that "we came together not in the party's interests but in the national interest" line they kept coming out with!) -- while it was the right thing to do, probably, they have paid a heavy price for it.