I was reading a lot lately about shops that require giving out your cell number, and then having to endure call after call until they finally give up on you. I thought I should share what I do. This is not spam, and I do not work for google. I have had a gmail address since they first launched, and it has served me well. Recently, Google bought a company called Grand Central, and now offer anyone with a gmail account to get a free online phone number. This number can be set to ring to several different phones, or none at all. Mine forwards to my cell phone. The best thing is that you have the option to block callers. Once I start getting calls, I can go in and block the number so that the receive a message that my number has been disconnected. It also digitally records your voicemails and some other cool stuff.
I use it in mystery shopping when I have to give a working number, as it is a real number that is mine. I just have the ability to shut it off, block people, or have it in "do not disturb" mode without affecting my real cell.
Hope this helps someone. I've been using it for a couple of years. I don't know why I didn't think to offer this advice before.