Will spammers force me to close the forums?

This morning I checked the email and I found that a lot of spam have been posted in the forums.

This is because I like the idea of "openness": why someone has to register to ask a question? So, the forums are open to anyone to write their thoughts... and bad people are exploiting this for promoting their websites...

Until now I was using subkismet as spam protection, I changed to reCAPTCHA, that's more difficult to read, but let's see if it is more effective