Not necessarily.  There are a lot of members on DT who do nothing to actively stop scams.  Take a good look at who's on DT1 & DT2, and you'll see a lot of them aren't even here all that much.  There really aren't that many members tagging scammers, and it's not our job to do that.  I do it because I think it's a good use of the weight of trust that a DT member can leave, and if DT members weren't tagging them we'd have total anarchy on bitcointalk.

Having said that, I got put on DT2 because I was tagging shitposters (I don't do this anymore) and account-selling scammy folks (I still do this).  But I think a lot of DT members are made simply because someone higher in the hierarchy trusts them--and that's completely valid IMO.