[ryansan]

I always thought it was good to compress first because you can more easily avoid frequency attacks. In that way I think it's better to compress then encrypt.

EDIT: That and you get to encrypt a shorter data stream. I realize frequency attacks aren't as much of a concern these days but it's just the first thing that came to my mind.

[unsignedint]

Also, some encryption systems integrate compression; like OpenPGP -- it supports ZIP, ZLIB, and BZIP2. So in such case, it may well be just sufficient to encrypt uncompressed data.