Okay, here's some not-so-official-yet-rather-reliable info:
I went to the IF-concert in Tampere yesterday (more to see Soilwork and Pain, but anyway). After the gig (which was great - my arms and neck hurt like hell), I met several guys from the band at a local bar and had a little chat with the very cheerful Anders Fridén. I asked him about the disappearance of the forum and his reply was something along the lines of:
Yes, we shut it. There was too much shit going around, people who don't know us talking fucked up things about our lives, etc.
I agreed with that, but asked why they didn't just try to moderate the discussion there, where Anders replied something like:
That would be dishonest, we don't want to prevent people from talking shit, they just need to talk shit at someplace else.
I tried to ask him, if he realized how disappointed some of their fans were, but he simply said that:
The ones to blame are those few, who had been insulting the band and the real fans will find a place somewhere
He gave me the impression that In Flames (or at least Anders personally) was very fed up with all the internet-communication regarding the band and wanted to turn back the time to those days when artists didn't necessarily need to be in any contact with their fans, except for the gigs (and he said they had enjoyed the whole tour a lot) - despite the lack of realism there, I have to admit they did the right thing, if the forum really was bothering them that much. Perhaps they just should have done it a few years earlier (but that's hindsight)...
About the lack of a pre-warning or an explanation, he just said that there had been too much hazzle regarding their explanation for the previous forum-closing, so that they just decided to exterminate it all and forget about it.
Note that we were both somewhat drunk during our small conversation (and some too good-looking girl was stealing the majority of Anders' attention from me) and thus the above sentences should not be taken as direct quotes.
-Villain (doc T. as an undercover IF-spy)