Been a while since I've heard about them. Not sure if I redeemed all of these so they may still work https://www.humblebundle.com/downloads?key=b227qZU5huqV
I didn't claim anything from it, but if there started to be a diversity of accounts suddenly registering the keys it wouldn't surprise me if it raises flags somehow.
Could be lots of different IPs loading the page but I still don't see why they'd worry about that.