To me PM, seems to have that happy state where there are a goodly number of people at different levels of knowledge and expertise and a culture of being both helpful and meta-helpful - teaching people how to ask good questions rather than heavy flaming for poor netiquette.
Also - there appears to be a reasonably steady influx of new people asking questions, learning and growing, which presumably helps avoid stagnation.
I found it interesting that you found the embarassment of asking here such a strong disincentive to ask "stupid" questions and a help to having the knowledge stick. Ironically, I suspect the helpful culture here has that effect more strongly than a newbie-abusive culture would (although the latter might have the same intention, but achieve it less well).