Please don't make me pick an account name
I just got through registering with yet another website. It was a pain, because they made me pick an account name.
There's two problems with account names. First, they matter because they're public identities; they say something about you to onlookers, so you care what your account name is. Second, at least for me, they're hard to come up with.
My first and second choices are almost always taken; three letter names usually go fast, if the system even allows them, as do common first names. I feel that my last name, while pretty unique, is too long to make a good account name, and I've never come up with a distinctive online handle.
(I sometimes envy people with short last names, especially if they have a first initial that goes well with it. Not that last names are perfect; among other things, they tie your real world identity to the account, and not everyone is willing to do that. And people's last names change every so often.)
The result is that any time I'm asked to come up with an account name I get to flail around trying to come up with something that is both untaken and something that I'm willing to be known as. Often I can't change my mind later and rename myself, so I'd better be really confidant about whatever I pick (which is hard when I'm making one up on the spot). Unless the service is very compelling, this can be enough to make me go away, because it is simply too much annoyance.
I suspect that I am not alone in this, so I have a simple plea to people: please don't make new users pick an 'account name' unless you really truly need such an identifier. If at all possible, let people supply just a name or an email address. And understand that if you ask people to make up account names, you are asking for something hard, especially if you do not let people change them afterwards.