random |ˈrændəm|
adjective
made, done, happening, or chosen without method or conscious decision : a random sample of 100 households.

So ‘random‘ means a selection from within a range of perfectly equal possibilities. That sounds about right doesn’t it, well lets consider the definition of ‘arbitrary‘ now for a moment:

arbitrary |ˈɑrbəˌtrɛri|
adjective
based on random choice or personal whim, rather than any reason or system : his mealtimes were entirely arbitrary.

Wow, now that sheds some more light onto how I’m feeling. Randomness is a part of arbitrariness, but it includes the whimsical aspect of human choice, not the mechanical aspect of randomness which is much more mathematical and based on probability. It still sounds pretty silly, so lets give an example:

“This blog post was very random.  I loved it.”

Well, was it a random selection from any number of existing or potential blog posts that could have been posted, or is it more likely that is was an arbitrary post, chosen with little regard to the consequences or impact it would have from any number of potential posts that could have been written. Think about it.

–Tom