Disable right column in user-settings

[HenrikHansen]

Is it possible to let the users only be able to put blocks on the left and center column?

For sites with fixed-width styles the tables are expanded if
you have blocks in all columns, and it would be nice that if you were
able to control the site so that width always stays fixed.

[Brian]

I'm sure that would be possible with some hacking of the files, but there is not really an easy way to do that currently.