These spammers try everything

Wow these spammers are tenacious. I woke up this morning with a bunch of spam sent through my contact form, which was built specifically to avoid spammers getting my email address. Interesting that they'd bother hitting this, since it's clearly just designed to send mail to me alone, not a wiki or anything.

I wonder if this is being hit by human beings or by robots? I've put in a rather easy question to test this, and I'll see if I continue to get spammers this way. If it's human beings (presumably third-world cheap labour) it would be very difficult to avoid.