i'm not so sure that obama's long ad is such a good idea. not that i think it will matter much at this point, but who wants to sit through a half-hour paid infomercial about any candidate? obama's appearance on the daily show could be entertaining, but a half-hour advertisement just sounds boring.
paradoxically, the only way this ad buy could make a difference in the election is if it spurs a lot of protest by the mccain camp. that makes the infomercial an "issue" that the talking heads can talk about, thus letting the obama campaign dominate the message of the news coverage immediately before and after the ad runs. as ken goldstein says "Every day that people are talking about Barack Obama's infomercial is a day that John McCain isn't getting his message out."
luckily, mccain supporters are already crying about it. so what otherwise might have been a waste of obama's money might end up benefiting him simply by making mccain piss away one of the few remaining days of the campaign.