This happens if I try to register.
One myBB user told me it's a plugin/mod and looks like it prevents users from registering. And I'm definitely not a spammer, so it must be a mistake. I'm sure I'm not the only one who have seen this message.
So please watch out if you don't want to lose some potential new members.
Usually the problem is the fact that mods check usernames against the sfs database and even if that username is in the database once then it blocks the registration. That is the number one issue for false positives. If you disable username checks or modify the mod to take into account the number of times a username/IP/Email is in the database and/or last seen dates then it will massively reduce the issue. The issue is more to do with the mod rather then Stopforumspam.com itself. It is up to mod authors how they use the data and the information available but alot don't utilize everything available.