Google Voice FAQ- http://support.google.com/voice/bin/answer.py?hl=en&answ...
Correct.
However you can (I did) do this:
1) Move the landline to your cell phone provider (assumes you have a family plan, if you don't convert to one for the time necessary to do the other steps).
2) Once the number is at the cell phone provider you can transfer it to google voice (and get rid of the family plan if you didn't have one). Took a few weeks.
3) You can buy an http://obihai.com/ device if you want to be able to hook up a traditional POTS phone to get the calls. Or you can just make and receive calls at the google voice website.
Note: I did this with the cell phone provider being AT&T. I would assume it will work with other cell providers but it does with AT&T.
You're wrong. Walk into any wireless carrier store, grab the cheapest pre-paid phone, transfer your landline # to the prepaid phone. Log on to Google Voice and now transfer your mobile number.
I did this for my parents who were still using Vonage. Works flawlessly.
If my inlaws wanted to get rid of their landline and get individual cell phones and needed their old number to transfer out, they wouldn't port their number to Google Voice and then forward from Google Voice to their cell phone.
I'm also not sure if paying $10 / month is attractive to consumers, but that's just speculation!
The price might be a little high for what it's doing, but if the idea is to eventually phase out your landline number, this could be a good way of doing it.
Almost every one of my non-tech friends uses it as well.