I seem to get caught about eighty percent of posts that I write, which given the whole 'random' thing which is supposed to make Captcha's better, really doesn't feel so random to me.
Also, when Captcha asks me to add umlauts to my letters, or gives me things combining a little something from everywhere on my keyboard (Seriously, what was up when I got 'g%fers~) when the e had an accent on it, I just want to destroy whoever came up with the system and let him rot. I once had to cycle through I shit you not twelve different iterations before it gave me one I was actually capable of producing with my keyboard.
And to add insult to injury, I've seen just as many spams as I ever saw here. We didn't seem to have a significant spam problem, so either I missed the memo where we'd been overrun, or it's entirely unnecessary.