Twitter isn't the most reliable service out there. Today I signed up to follow a friend who is too lazy to type more than 140 characters at a time ;-), so doesn't blog.
While signing up, the CAPTCHA didn't show up. After several page refreshes I took a look at the source and it is using reCAPTCHA, which is all nice and good, but for some reason my wonky DNS server couldn't resolve the address of the reCAPTCHA api server :-(. So finally I looked it up with OpenDNS:
dig api-secure.recaptcha.net @126.96.36.199
And hardcoded it in my hosts file (this will be really nice when they move servers and I forget that it is in the hosts file and start to wonder why it doesn't work again :-)).
The morale here is that when you depend on an external service, you will have some problems if that service goes down (and
down can be very tricky to define - for example reCAPTCHA wasn't down for people using a sane DNS server, it was down just for me - this means that even if Twitter used a network monitoring solution to check the availability of reCAPTCHA, it still wouldn't have done me any good).
PS. It was asking for my e-mail password to spam my friends. Yeah, like that's going to happen...