I do not want to fund Obama's effort to foist what I consider to be bad policies at best or evil policies at worst on our nation and world. Why should I want the tax dollars of my political opponents to do the same?
I suppose he is raising bucket loads of private cash and to take public dollars would actually hamper your effort to become president, so you opt out. Perhaps (and I guess likely) but isn't that what democracy is about? The public at large is already speaking up and being heard about who they want as president.
Also, is not Senator Feingold a part of that old system you refer to when John McCain opts into public financing? Do you slur Senator Feingold when you use that tired old cliche, or is there a Feingold exception?