Sadly, the use of VPN services can get you banned from many sites for absolutely no reason.
Steam, Amazon, Paypal, and many other companies are fast to lay down the banhammer if you use a VPN, and it's pretty depressing. Even if I'm not using it to bypass any sort-of region locking, they disallow it.
amazon? proof? i order stuff from amazon all the time...
if you're using a "free" VPN, e.g. HotSpotShield, then i could see you being blacklisted for abuse.
other than that, some forums are just straight up crazy about their blacklisting policies... and basically, fuck them for not understanding security concerns and learning how to mitigate abuse without cutting off access entirely.