[Smilin']

It's very likely that mild preferences don't have equal weight. Voters who care about an issue a lot will inform themselves about candidates' positions; voters who are almost indifferent won't bother. In the end, the small minority with a strong preference could easily end up with too much influence. Think pork barrel spending--the problem is precisely that there's an incentive to take a tiny but from a large population of taxpayers and funnel it to a small minority who will notice.