Happened to me yesterday when logging to flickr via yahoo.
Yesterday I had to go through a moving captcha when trying to log into flickr. I got redirected to the yahoo login webpage where I copied and pasted that 20 something random characters yahoo had me working on for a cumulative time of an hour (I had to tweak pwgen to get some reaaally random stuff and yet see yahoo rejecting it because "too easy" and then wait for an hour or two before I could try again).
Then they had me confirm I was not a bot by asking me to type the moving letters in a captcha.
Yesterday I had to go through a moving captcha when trying to log into flickr. I got redirected to the yahoo login webpage where I copied and pasted that 20 something random characters yahoo had me working on for a cumulative time of an hour (I had to tweak pwgen to get some reaaally random stuff and yet see yahoo rejecting it because "too easy" and then wait for an hour or two before I could try again).
Then they had me confirm I was not a bot by asking me to type the moving letters in a captcha.