"Over one-third of Americans (37%) say that television ads are most helpful in making their purchase decision while 17% say newspaper ads are most helpful and 14% say the same about Internet search engine ads. Radio ads (3%) and Internet banner ads (1%) are not considered helpful by many people. Over one-quarter of Americans (28%), however, say that none of these types of advertisements are helpful to them in the purchase decision making process."
On the bright side, 9% say they don't ignore ads.
-- Harris Interactive, July 1, 2009 (pdf)