In order to maximize compatibility for macs (Because say, every macbook of a certain type has the same hardware), they did something you'd normally see on a console, they made every source game update to one specific engine, instead of being scaled over several, and without bothering to fix any errors that may arise in the sourcesdk or source 2009 itself, they just simply updated everything and it broke everything. For well over 6 months now, they did nothing and instead just repeatedly pushed out more and more content for mac, neglecting the obvious gaping holes in using 2009, disregarding several topics that spanned for tens of pages for well over 4 months, and simply deleted them as they popped up, and when their 'volunteer staff' popped a response, they simply quoted the FAQ, which had absolutely NO helpful information whatsoever.
You want some sort of source that it was actually broken? Ask Strider, or anyone else it was broken for, for that matter, I would have a more valid source myself, if the threads hadn't been locked and removed left to right, now all that remains is a couple 3 page threads, which of course is little more then 10 people, and that isn't much of a source.
All of this information would have been available right from the start, but instead i posted a witty response which i figured most people would have gotton, but i guess not.
(EG: For biased people who say ati sucks and nvidia is the best, I often post "What's that? I can't hear you over my fried Nvidia card, I made the fatal mistake of installing the latest drivers, whoops!", or people who prefer xp over windows 7: "What's that? I can't hear you over my DirectX 11", you get the idea.)