I guess what's wrong with it is that the candidate with the most support should get the most votes, not the most money.
Look at it this way.
Say I support candidate X and I want to help get him elected. Is it OK if I talk to my neighbors and encourage them to vote for X?
Is it OK if I spend ALOT of time doing this, even meeting strangers and encouraging them to vote for X?
What if I wanted to buy the supplies necessary to craft signs, t-shirts, buttons, stickers etc. showing my support for my candidate?
If some of my friends/neighbors can't drive and live far away from a polling place, would it be OK for me to spend election day driving everyone like this to and from the polls to help them vote?
Would any of that be wrong? I don't think so.
But let's say that I live in a non-competitive state. It doesn't matter what I do in NY, because NY's electoral votes are going for the Democrat anyway, and candidate X has no shot here. I want to help, but I can't just move to a competitive state for the election season.
Or maybe I'm incredibly busy at work/school. I would love to take time to do everything related to getting out the vote, but I just don't have the free time.
But I do have money.
So I donate money to candidate X, and his campaign uses that money to do all the same things I would do on my own. It costs money to print yard signs. It costs money to hire people to go around their neighborhoods and encourage people to get out and vote. It costs money to get people to stand outside all day and encourage unregistered voters to register. It costs money to do everything a campaign needs to do to win.
So if volunteering your time is OK, but you don't have time or the ability to volunteer, what is wrong with enabling others to volunteer so that your will can still be expressed?
Really, volunteering and giving away money are the same thing. Usually you work for a salary, but in the case of volunteering, you work for free, you forfeit the money you could've made because your candidate is more important to you. In the case of donating, instead of sacrificing potential earnings, you're just sacrificing realized earnings. Both is a free gift to your candidate.
And even if candidates' spending was capped, Obama would still have a huge advantage over McCain in this election because of the extra enthusiasm of his volunteers. Obama has WAY more volunteers operating out of WAY more field offices than McCain does. Take the money out of it, and McCain STILL is disadvantaged because Obama's volunteer force dwarfs his.
So then, for fairness' sake, should volunteering be regulated? Should each campaign be capped in the number of volunteers they can have? Should the state appoint x number of workers to each campaign and limit the volunteering activity of anyone else?