Many of my best posts(or those that got the best reaction) were made anonymously. At the time I wouldn't have made them if I had to use a name, because I was afraid of being wrong.

>Useful for suggesting more contributors than just Sling!XD/uSlingU?

That requires more sources of material to contribute.

>Good for a community with no vanity and attention whoring?

Yes, with some light moderation. Zero moderation and you end up with Usenet.

>Or promoting trolling and DQN behaviour?

I think trolling is only promoted as readily as the community bites the flamebait lures. I get the impression that on futaba trolling is largely ignored and/or embraced, if that makes any sense.