The Lib Dems, after years of having no say at all in government, are making changes to policy. If anybody on the left of the spectrum doubts that, just go and read the screams of rage from the Conservative press and blogs, from both activists and MPs, about the Lib Dems. To get any policy though, they're voting for a lot of largely Conservative policies. That doesn't make them liars, traitors or stooges; it simply means they're working legislators who are trying to do what they can.
On the other side, the Conservatives didn't win the election, and really need to learn to live with that. They're not going to get everything they want, and have to compromise to get anything at all through or it won't happen. That means accepting Lib Dem influence in every bit of legislation they want to pass. In particular, it means living with the fact that the Right of the party doesn't have as much sway as they would in a narrow majority government.
On both sides, I suspect there's a fair degree of the grass roots keeping pressure up to ensure their side fights their corner hard.
I can appreciate the emotional view that would prefer the Lib Dems to just say "no" to everything they didn't like. However, that would likely have disastrous consequences for the Lib Dems in the long term, especially if they started doing it now after they've managed to get themselves blamed for the whole of the higher education funding changes. (Despite managing to reshape them into something close to the graduate tax that was policy all along. Shame it's a tax with a lifetime cap, but that's the compromise.)
As suggested by pseudomonas (obviously this is just an arbitrary and subjective quantification, but it might be amusing):
How much influence are the Lib Dems exerting on government (where 0 is none of their policy, 13 is pure Lib Dem policy)
How much influence should the Lib Dems be exerting on government (where 0 is none of their policy, 13 is pure Lib Dem policy)
The Lib Dems have 15.7% of the seats in government, 57 out of 363; and nationally got 39% of the votes cast for the Coalition parties, 6,836,824 out of 17,540,578. That's 2.04 and 5.07 on my scale, which goes to 13 to make those close to round numbers. I was going to make the scale go to 11, but thought that Spinal Tap references were more amusing than helpful.