To show you how big the community is, currently they have a registered user database of 1,427,121 users! (with 95,754 of active users). But managing the community is not that easy, especially considering the community expansion + not everyone who register at Ubuntu Forums have the same good intentions (yep, apparently there seems to be massive "SPAM campaigns" going on too :D, not funny though).
So as a result, Isabelle Duchatelle, one of the UF council members, in her personal blog yesterday announced that from now on, the newly registered users will not be able to change their profile information (such as links, etc) until they've posted at lest 50 posts. This actually makes sense and according to her own words in the UF announcement thread...
"... We will be taking away profile customization from users having less than 50 posts. We are quite sorry about that, but currently it takes at least one hour from 2-3 persons, each day, to clean profile spam. New users register only to fill the account with spam links, pics and things... we are quite tired of spending so much human resources on so little interesting tasks"If you're a new UF users, then you don't have to worry about anything because as soon as you have 50 or more posts in UF, the system will automatically update your user permissions thus you'll be able to add/change your profile information. But since it's an automated task, which updates the database once an hour, Isabelle says that there could be small delays but you should see your permissions updated within 1 hour at max.
You can read more from this Official announcement thread in Ubuntu Forums.