You have to feel some sympathy for David Laws.
I know as a Liberal Democrat member I am bias, however he gave up a job in the city (where he was earning a hell of a lot more than he is now, having been a Vice-President of JP Morgan when still in his 20s) to become economic advisor to the Lib Dems with no prospect of being in power. He hardly fits into the "only in it for themselves" mode that most politicians are accused of. It appears that he has been the subject of a media witch hunt since his rise to prominence as a key member of the Lib Dem's negotiating team.
At the same time though rules are rules. In the housing expenses rule book it clearly states that rent should not be paid to one's spouse, a partner or a family member (including civil partner). Although David could have claimed a lot more over the 8 year period and could have benefited more personally from the issue his desire to keep his sexuality a secret means that he did break the rules. As a result I don't think that his position (particularly as it was within the treasury) was tenable, particularly with the feeling about the expenses 'scandel' still fresh in most voters memories.
The greater tragedy in my opinion though is that he has hidden who he is for all of his life for fear of victimisation for being homosexual. I can, however understand his desire for privacy and hope that he will now be able to get this and continue to be a vital part of the Liberal Democrats.