Don't forget that the game was actually playing fine during the first hours of gameplay (excluding the horrible introduction in the beginning).
I was one of the early adopters and found the framerate to be perfectly acceptable at first. There was no way I could have tested the game reaching further into it to see the problems. Furthermore, my slow playing style, as I tend to stay in one location for a lot of time or just wander around to admire the landscape, helped me to actually put a lot of hours into the game without running into the major framerate flactuations.
If the problem was clear from the beginning I would never encourage people to get the game. It's not a clear case like Codemaster's F1 2011 where that game was clearly inferior in all aspects compared to the xbox version from the start.
I don't blame people, but even though it may have been decent at the start, even then, as lensoftruth and DigitalFoudnry reveal, near Riverwood, it's constantly fluctuating in the upper 20s and I can certainly feel it. In the tundra near Whiterun it was decent enough... lucky enough that nothing needs to really be rendered in the tundra.

Anywhere outside of really barren areas or in small interiors, however, and even then the problems are noticeable, but yeah, at the beginning, it seemed okay. It wasn't at a constant 30 fps and that ticked me off, but I thought it wouldn't get any worse than that... then I took a trip to the fall forest and Morthal, started exploring dungeons other than burial mounds, and in general simply left the tundra. Still not happy with a fluctuating upper 20s framerate, but it was okay... a bit choppy and a bit sluggish, but okay. In any case, the truly bad part is what it indicated... the engine was already struggling even in less demanding areas, this game clearly isn't very well-optimized for the PS3 and if only we could see it through the early-release hype and honeymoon period... and that's just the base performance. It's utterly unplayable garbage for the people unfortunate enough to get the long-term issues with lack of memory consideration.
..and yet they sold it at the standard retail price. Business as usual.
Indeed. You know... the PS3's CPU is superior to the 360's (partitioned differently and requires a different rendering path and specialized coding language, but that's standard for a completely separate platform) and Skyrim is a very CPU-intensive game... makes me wonder. Skyrim could have been great on the PS3, what with the PS3's greatest asset, its CPU, coincidentally managing to match Skyrim's most demanding hardware component and Bethesda still not taking advantage of those capabilities...

Money's all that speaks.