Here is a Raise datapoint using Visa/Mastercard GCs. My account got suspended the weekend they were doing the 8% on Mr Rebates. I just called in to get it unlocked and they told me it was because the system detected that I was using a prepaid card and that's not allowed. Now, I also ordered one the day before, and then three the next day - once at work, once on my phone on the way home (website not app), and once at home, and each time had to get a security code. I thought it was going to be because of that.
Just thought I'd share my experience.