Facebook, seriously, WTF?
I mean, what the hell is that? Some kind of deformed Pac-Man? The Man in the Moon?
I’ll tell you what it is — some unrecognisable blob, that’s what.
And I bet they knew, too. When I clicked “Try different words”, the blob was replaced by the word “unusable”.
My bet’s on “to”. Captchas are difficult because the bots are too good.
@Alexio: They don’t need bots. They pay people in developing nations pittances to solve CAPTCHAs in a system similar to Amazon’s Mechanical Turk. Why spend money on perfecting an AI that can do this level of OCR when you can get a million CAPTCHAs solved for low 4-figures?
Hmm… there’s an awful lot of people out there that make life hard.
What are the alternatives to CAPTCHAs?
1. textual questions like “what color is an orange” (Ubuntu forums)
2. sending instructions in an email (instructions that require human thinking, with a delay, perhaps?)
3. tracking IPs that generate large numbers of requests (as Daniel has done)
4. putting a time limit on captchas/questions to make it more difficult for The Turk and friends (must have “click to refresh” button)
5. [This is awful: ] demanding a mobile phone number (like youi.com.au)
6. The ALDI/GE Money approach: no email address, no web form, just a phone number and a postal address.
Perhaps it’s a Unicode character?
If you have a high-target-value site (facebook, hotmail, wordpress, phpbb et al) you’re going to need a better human-detector than most sites, and as Greg points out, if you’re just trying to detect humans there are mechanisms available to prove you’ve got access to humans. Low value sites can get away with such methods as having a text box labelled: Type in the word “Orange” (codinghorror.com had the same word – Orange – as the anti-spam field for many, many years).
It’s the same-old problem with spam: the unit costs are low. Push up the unit costs (perhaps charge $10 for an account, and refund that after a month or two of legitimate activity) and the whole problem goes away. Or, as Nick mentions, a mobile phone number – they cost $ to acquire.