Why you shouldn't compress SQL Server data and log files
I am in awe to what Ken Henderson manages to write everytime. Let alone his books on SQL Server Internals or the MSDN articles he writes. It's amazing to just read his blogs ... The interesting part is it is free :).
I know people quote performance issues whist using compression for the data and log files. But here is a very classic and fantastic reply *technically* correct to take to neck deep into the problem. A worthy read and a worthy blog to add to your favourites.