Ask HN: Twitter profile picture not showing if logged out

i just mad a curious discovery. when i'm logged out of twitter and make a search, the profile pic of some users is not showing up (including mine). when i click on the user to see all his/her tweets, then i can see the pic. check this link as an example (you need to be logged out of twitter):

http://twitter.com/#search?q=simonstahl

any ideas what the reason could be for that??

i wish you all happy holidays!