I hope Craigslist/eBay are smart enough not to accept your numbers when you have to give a phone number to verify your account (to stop spam/fraud). It should be possible for them to block all numbers not allocated to landlines or cell carriers...
We will soon add a mandatory step to authenticate the phone number used to sign up for Roller (just like Craigslist/eBay does). It is our #1 priority to prevent spam/fraud. Thanks for the comment.