On Tuesday, Oct 23 got a call from (886)546-3793 (which I noticed also happened to another caller on this list) on my cell phone. Did not answer and they did not leave a message. Today (two days later, received a call from (415)562-2366 also to my cellphone. When I answered there was no one on the other line. I'm located in Canada, so it looks like they are being fairly indescriminate about who they are targeting.
Received call from this number again this morning. They must have the latest "DNC" programming: as soon as their computer dialer sensed that my business line calls were being forwarded to a cell, it hung up--that's what the programming is supposed to do. These dubious "Yellow Pages" telemarketers (whoever they really are) pull a pretty good con. They could confuse someone unwary, which of course is their intent. I've been phoned by them in the past repeatedly. As noted in other comments, the callers often have thick foreign accents (I think they are Indian too) which are hard to understand. Hang up on them and block their number if you need to.
Like "Mildly annoyed - 25 Oct 2007", I got calls from 1-866-546-3793 and 1-415-562-2366 too. Between these two numbers, I received at least 4 calls within the past two days. On all occasion, the callers didn't speak. I figured they were just more telemarketers' calls, so I just hang up after announcing my business name and said hello.