Accordingly: " Seventy-six percent of all U.S. adults have signed up for the FTC's Do-Not-Call registry, according to Harris Interactive, MediaBuyerPlanner reports. That's a significant increase from January 2004 when 57 percent had registered."
I'm betting that the other 24% of adults, who are not on that list, will add their name soon.
I also think it's a matter of time when a similar "Do Not Call" list emerges for e-mail direct marketing (except when there's a pre-existing relationship between the company and the customer). But that will take some time.