On the face of it Competitive Intelligence is about email, but the title is a better indication, it is about [strategic] market intelligence.

This article - Seven Rules for Achieving Higher Online Survey Response Rates - does what it says on the tin.

Simply watching what is happening online is an excellent way of gleaning information, this article - Seven Buzz Monitoring Sites To Watch - gives some excellent tips on the software that is available to help.

This one - The Armchair Sleuth: Competitive Intelligence Via Search - takes market inteligence to a whole new level - but don't think this isn't what the major players do.