It's a convenience but also, a degrading factor to the community...
PROS: It keeps spam in a centralized point and limits how much spam gets into the other subs; it provides a nice place for new comers to ask a question and get a feel to how the community responds to varying levels of questions BEFORE they decide to actually sign up for an official membership; it provides a place for people to test out their "helper" skills within the community...and at times really weeds out who knows their stuff here, who doesn't know jack squat and the technical levels the core members are that venture into the area.
CONS: It cheapens the experience of iMore, creating an almost "catch all" to traffic here on the website...preventing people from actually putting forth a legitimate effort to become a part of the community, and just scatter shot random questions and thoughts in there; Being that it is the first place most people see on iMore, when you go in there, at times it looks like such an amateur offering, mainly reflective upon just how asinine some/most of the posts are; It's the HUB for the "I forgot my password" posts...and this, I think, is because you don't have to really put much effort into posting something like that vs. the effort it takes to sign up for iMore and go through that process...I think we'd get less of that traffic if the forum still required sign up even in the Q&A section.
...to me, if you're looking for traffic quantity, it's an effective method to garner such results...but if you're looking for quality, it's a total strike out and pulls away from what makes a community solid (in my opinion), and that is long standing core members who create more long standing core members through knowledge and member effort.