It is an
FAQ. FAQs are not about changing the rules; they're about answering questions about the rules as they
already are.
Let's go to another website, say
Newegg. Now, I want to buy a
new mouse. I see "Free Shipping." Hey, all right, I click "Buy." It even says on my receipt that shipping is $0. Then my credit card bill comes a month later and I see my credit card was charged $30 extra for shipping. So I contact the company, wondering why I got charged extra for shipping, when the website and the receipt say that shipping is free. "Oh," they say, "we decided that 'Free Shipping' really means, 'Free to charge you whatever we want Shipping.' We put it in our FAQ, but it would take too much time to update our website and receipts. Have a nice day!"
Fortunately Newegg doesn't do this; they're a great company and I love buying from them (No I'm not a sellout at all!

). If they did I probably wouldn't buy from them; I'd be constantly wondering what new rules they'd come up with while I wasn't looking, and how they'd bury it in a place I wasn't looking for new rules.
It's a similar problem with SR4. Though, granted, it's much less serious and dire in nature than the above mentioned scenario, it's still a bait-and-switch, and one I have no patience for. I have no idea when some line dev is going to decide that he suddenly doesn't like one of the books and decide to change the rules in an "FAQ" entry, and it's a turn-off because I really don't want to deal with either 1) having to constantly check the website and comb through all the FAQ entries looking for unknown and unasked-for rules changes, or 2) having to wing it when a player brings up a previously-unknown "FAQ" rules change in a game. Combine this with the historical insanity and game-breakage allowed into previous iterations of the "FAQ", and there is no doubt in my mind that the "FAQ" rulings, good or bad, will not have any place in my games.
FWIW, I agree that sustaining a thread
should not impact the technomancer who is using that thread to add to his dice pool, and is a very good house rule. On the same token, I also think that the same thing should apply to a mage casting a spell: if, for example, a mage is casting a Hawkeye spell, a spell specifically designed to make him see better, he should not be taking a -2 penalty to visual Perception tests for sustaining the spell, and for the exact same reason. Invisibility with Infiltration; Analyze Device with the device being analyzed; Magic Fingers with whatever skill is being Finger'd, none of them should suffer a sustaining penalty for doing what they are designed to do. Just like a technomancer with his Threaded Complex Form.
I would have no problem with changing the rules to include this; I'd even welcome it. The thing is, it is a rules
change, not a rules
clarification, and so it has no place in an FAQ, which is supposed to be a place for people to go when they don't understand the rules in the book, not when they don't like them and want them changed to suit the whim of a line developer.