More precisely, how many people have fiddled their expenses to the tune of a couple of thousands of pounds?
TheKnightWho is right. Despite it being quite a reprehensible thing to do, the amount that's claimed is only a fraction of the overall budget. The media pick up on it purely because of the size of the claims, and for what they've been claimed for (remember duck shelters?), and, moreover, because they're politicians ergo they're supposed to be in a position of up-most responsibility (

)
I'm not defending politicians, but this is a practice that's not going to go away so long as new loopholes are exploited on virtually a daily basis.