255 lbs is 102kg; in other words, if I sit on this desk, I'm getting close to the breaking point. Not good :(.
(INB4: yes, people do occasionally sit on their desks, sometimes without even thinking about it - e.g. when full of joy, or drunk. Also there's a good chance that someone at some point will want to stand on a desk to, say, change a lightbulb. Consider this especially if you're buing desks for a more public place, like e.g. your local Hackerspace.)