"About" and stickers

[wordchick.livejournal.com]

During lessons with my Russian tutor, every time I said про что-то, she would correct me, saying o чём-то. I thought these two prepositions were synonymous. Is the difference in register? Does o чём-то sound more educated?
Additionally, I've been reading Babel's Odessa Stories, and he seems to use a different form: За что-то. ("Скажи: Беня знает за облаву.") Is this criminal jargon, or maybe just local slang?

On another note, in the St. Petersburg metro, I saw a sticker with the following words: Олигарх тянет грязную лапу. Can someone help me parse this? I would have expected Олигарх тянет грязной лапой- The oligarch pulls with a dirty paw. I'm not sure what the former means, though I may well have misread the sticker.

I'd also like to thank everyone in this community. It's wonderful and supportive and it's become much more helpful as my Russian has improved. I don't know any dictionary that could supply all the shades of meaning that you all do or help out with slang. I am very grateful.