I think the idea is good. If we can have alternate URL (alias) of our galleries, why not to promote them?
For Herman:
At the moment, you cannot use special characters as part of URL (nowhere on the web!). So there are already restrictions implemented on username (used as URL alias). You are restricted to use only lowercase english (ASCII) letters, numbers and few special characters (dot, dash, etc.).
You don't need Russian, Czech, Greek or Hebrew keyboard. ;-)
For Wim:
I am pretty sure, nobody would remember the basic version with sequence ID.
BTW, I am not Facebook friend too, but not everything that comes with Facebook is bad. ;-)
For Roar:
Good point, ID is persistent, whereas alias chosen by user need not to be persistent. But it's under my control. If I ever use my alternate URL with alias as a link somewhere, I will not change it later.