Okay, just so people know what's ACTUALLY going on: reCaptcha was added because people were having their accounts with more valuable pets targeted and stolen; the data was being mined through user and pet lookups. This is possible because Neopet's security is a joke. The official story is a form of DDoS disrupting the servers, because TNT would never in a million years admit that accounts are getting hacked left right and center, bad for business. reCaptcha will help with this issue, but it's a bandaid solution at best.
My best guess RE: the current site crash is that they didn't upgrade the serves to properly handle all the extra load coming from the reCaptcha pages; either that or it actually is a DDoS now because the bots that would normally cause minimal lag trawling through lookups are getting stuck, and don't have reCaptcha sensing to self-shutdown, so they just keep trying to refresh the page and mine the data.