Revivio sent multiple emails with the call to action being a sales meeting and the chance to receive a free stereo. Muliple emails that reinforced each other were backed up by direct mail and telephone calls. The campaign had a 60% response rate and most of it came from email because supposedly they "were short, concise and punchy" (according to Revivio). They used a combination of in-house and purchased lists. Revivio also concluded that they're work in establishing their brand through online and offline ads (eg: Forbes.com), paid search and newsletters aided the success of this campaign. The other interesting item is that the free stereo wasn't the winner - it was the persistent marketing effort from all different angles that typically won the prospect over.
Conclusion: Don't use a single marketing channel for a campaign - think integrated marketing and see better results.
PS - Hey Revivio - if you see this, I'll take a free stereo (Let's see how well Google works!).
PPS - While were at it Revivio (assuming that you happen on my wee little blog), why not add a blog to your marketing mix?