[selven]

And this is why captcha's aren't that effective. They don't slow organized malicious hackers who can simply hire a third world worker to solve them for $1/hour, make a botnet make its victims do it like here, and so on. Meanwhile, many people are actually having trouble solving them.

[hga]

Agreed, although I'd quibble about the use of "that" (effective). They do set the bar fairly high and therefore stop a lot of "casual" vandalism and spamming, at the very real cost you note.