Every time you make a better lock, you also make a better thief. This means that there are spam bot programmers out there specifically figuring out ways to work around recaptcha. My company will be releasing a non intrusive product that will categorically prevent anything that is not human from submitting forms as well as verifying the validity of email addresses in real time, checking for spam, honeypots/spam traps, frequent complainers (reports spam often) and more…but we’re a few weeks out of release. We’ll be calling it ListDefense. If you’d like, I can place you on our notification list to let you know when it’s released so you can check it out when it’s ready 