It leads to some of the issues they've had in America. First of all you make certain forms of ID a requirement, then you make it harder for the people who will vote for the other lot to get those certain forms of ID. Bingo, one successfully gerrymandered election. It's why a couple of US states have been declared as no longer running properly democratic elections by international bodies. It makes it harder for individuals to commit electoral fraud, but it actually makes it easier for governments to.
In any case, most of the electoral fraud cases in the UK in the last decade or so have involved postal voting. It's pretty much impossible to prove the person who stuck the letter in the post box actually was the person who was supposed to have done...
I still think we really need compulsory voting combined with a 'none of the above' option. That would make our elections much more representative at a stroke.
