I can think of five factions destroyed by DBs, though I wasn't here for all of them. Ched's test faction, Youngblaze's bank, Xerxe's faction, Helvete, and one of the admins banks. The DB spree a little while ago was mIsch3vo's (sp?) work; he's the one who destroyed a cheaters faction-- and nuked SA twice if I recall correctly. Other factions, such as MMCP (no offense David) and Calculating, were never really at risk in the first place.
DBs are essentially too well known to be faction killers anymore, unless there's only one member who can be caught off guard, as was the case with Helvette.
They are however a great way to make a name for yourself. And, in the case of Vulpes, to scare the living hell out of a few people.