David Streitfeld, in today's Los Angeles Times business section ("Hanging On After The Big Hang-Up"):

In coming weeks, households can expect to be deluged with phone solicitations as telemarketers try to establish relationships before the registry goes into effect. The FTC already is getting reports that telemarketing call volume has soared. And after Oct. 1, those who haven't signed up for the registry can expect a flood of calls as marketers zero in on them. [...]
[David] Surrey [call center manager for Grand Pacific Resorts, which places 10,000 calls per day] is hopeful that a lawsuit will stop the registry at the last minute. And if that doesn't happen, he expects other methods — e-mail, for example — to blossom. "It's not like we're passing out pink slips saying, 'On Oct. 1, half of you are gone.' " [...]
[T]he widespread presumption is that all those not on the registry will, as [Sterling] Edens [who runs the call center for Welk Resort Group] puts it, "get overwhelmed with every type of telemarketing call imaginable."
That will drive more people onto the list. Which in turn will increase the volume of calls to the dwindling number who aren't on it. [...]
If this industry is fated to disappear, the [American Teleservices Association] telemarketing association says, it will go down dialing.
'Until every man, woman and child in the United States signs up for a do-not-call list,' the ATA's [Tim] Searcy said, 'the opportunity still exists.'