(Update at bottom of post.)
TC sent along an article about a free service called Nomorobo that claims to block robocalls. He wondered how it worked: "If you're not bundled with everything together, how is your computer going to answer your phone when it rings? There's no connection between the two as far as I can see."
So I looked into it a bit, and I figured I'd post (a mildly edited version of) my reply to him, since it seems like potentially useful information.
According to an article in the Baltimore Sun, you have to have VoIP service:
Only customers who have VoIP service with AT&T, U-verse, Cablevision Optimum, SureWest, Verizon FiOS and Vonage can currently use Nomorobo. I was successful in setting up Nomorobo on our home phone. Now we will see how it works.
However, looking around elsewhere, it appears it's not quite this restrictive. According to GadgetReview, for example (and see the FTC link below, too):
The only drawback is that the service requires simultaneous ringing, which you can’t necessarily get depending on your provider. It’s easy enough with VoIP or landlines, but cellular connections may or may not have the service depending on which one you have.
Simultaneous ringing appears to be a service that allows you to specify one or more additional phone numbers that will ring when a call comes in on your main phone number.
So, Nomorobo doesn't have anything to do with your home computer, and further, it looks like it's not so much that Nomorobo is in between your phone and the outside world as it is operating in parallel, if you see what I mean.
The Baltimore Sun article indicates that you have to get into the habit of not answering your phone on the first ring, because that's the amount of time it takes Nomorobo to analyze the incoming call. If it's spam, you won't hear a second ring, it says there, so I guess it's essentially lifting the phone off the hook and hanging it back up, as it were. Sort of like if you had an extension in your house, and someone else grabbed it up and banged it down before you could pick up the phone next to you.
Given that the company won an FTC prize, I'd say it's probably on the up and up, so there's probably no harm in trying out the service, if you're curious. Visit nomorobo.com to have a look. It appears that they'll want your email address, which may put some of you off, but if robocalls are enough of a nuisance to you, maybe you'll find it worth sharing this bit of personal information. The service is, as I said above, free.
Admittedly, I'm probably not going to sign up. I pretty much never answer the phone if I don't recognize the incoming number, so robocalls aren't much of a nuisance for me.
. . . . .
A second approach I use, on the rare occasions when I do pick up a ringing phone without checking CallerID, is to say "hello" once and once only. This doesn't stop robocalls, since they'll just start playing as soon as the connection is opened, but they're easy enough to hang up on immediately, without guilt. But for telemarketers, it works great, because they almost never start talking until you say "hello? HELLO?" I think most of them have some sort of software or other gadgetry that notifies the (sub)human on the calling end that a live person has picked up, and that software or whatever appears to work basically by listening for additional sounds* after the initial "hello." So, I say "hello" once, wait for two or three seconds, and if there's just silence, I hang up. Works like a charm.
* Or maybe it's listening for a short initial sound, then silence, then more sound, so that the telemarketer doesn't start talking to an answering machine or voice mail. Odds are, in the latter case, that the outgoing message is considerably longer than the one or few words the typical live person utters when answering a phone.
[Update] Other resources for dealing with unwanted incoming calls are listed at the bottom of an interview with Aaron Foss, the inventor of Nomorobo.