I think that was an early guesstimation image that's not totally accurate, it is bigger than the PS3 but not by as much as shown there.
In this video it looks so different to the teardown.
I would hope they would not guarantee it clogging up, would be pretty bad if it did! (Looks like they forgot a not there)
A blower cooler can be efficient, of course you can always find more efficient alternatives (except when you find the single most efficient one) but then you're often looking at more expensive alternatives. It's a cost/benefit/usage issue, if it runs cool enough and quiet enough it's good enough. We will know when the first consoles are out and being beta tested for later buyers.A blower cooling setup is so archaic by today's standards, especially in something big like a console. Very surprised Sony stuck with it seeing as it's not an efficient pathway for the air. It may well work but it's such an odd decision.
The original PS3's cooling system was also ginormous and people thought that would mean it's good but it was pretty terrible.