Finally, there's legislation afoot to force robocallers to knock that shit off.
http://www.pcworld.com/businesscenter/article/250053/fcc_cracks_down_on_telemarketing_robocalls.html%23tk.rss_news
"The U.S. Federal Communications Commission has approved new rules requiring telemarketers that use autodialed or prerecorded telephone calls to sell products to get written approval from customers before sending them the robocalls."
And apparently they've closed the "previous relationship" loophole. Whatever that means, in the context of buying and selling wholesale lists of numbers.
Now I'm sure the other trickery will begin - calling, letting it ring once, hanging up, then waiting for YOU to call THEM since you don't know who they are and think you missed a call. But at least you don't have call back the "one ringers". Anyone who does that doesn't deserve a return call.