They are most likely to be bots (the spam you have recently seen.. were they from new users or users that existed before the time you installed FoolBotHoneyPot)
FoolBotHoneyPot is also included in TAC (It stops 100% of spam bots from registering, but if they were already registered, then they'll still spam)
FoolBotHoneyPot stops 100% bot spam on the registration page (it also tells you a lot about the bots/humans ... including header information, proxy information, js information, cookies, how many hidden fields they get picked up by, if they get detected by AnyApi
Also included in TAC and to be used with FBHP is AnyApi, this is set up by default with StopForumSpam, Project Honey Pot Http:BL, FSpamlist, Spam Busted,Bot Scout ... up to 10 APIs defined by you if you should need that, to be honest, once FBHP is installed, additional API's are pointless, I just use FBHP + StopFormSpam for humans)
Also included in TAC is StopCountrySpam - to stop Spam from particular countries
No bots can currently get through FoolBotHoneyPot (It would requier a significant redesign for XRumer). If you still belive they have, please can you PM me your logs with FBHP installed, the username of the spammer and also find it in the FBHP logs (it will be there if the bot/human registered after the date that FBHP was installed)
I found a way that works for me. Formulate a CAPTCHA question that asks about something in the future. Spambots can't speculate about the future. They have to use existing data and there is no data for the future. For example, during the elections I asked "who will win the presidential elections?" There were only two choices that any human could guess at but spambots could not. After the election I changed it to "what holiday will you celebrate in December" and gave a list of choices. So far so good. I think the key word is "will." Bots don't have a will, they're programs. I've been spam free for over a year since I started using this method. I got the idea from Kier who said "try to think like a bot when you formulate your CAPTCHA question." Bingo!
I get a kick out of seeing 20 bots try to register all at once but can't get passed human intelligence.