m4/3 - no U.S. market penetration...yet?

I'm guessing this has much more to do with Panasonic and Olympus U.S. distribution strategies than with any cultural differences between American and Asian or European consumers.

Canon and Nikon DSLRs available everywhere in the U.S., even office supply stores (Staples) and discount department stores (Target). Two years ago when I bought my GH1 I don't think the camera was physically stocked at any store in the Boston area, including specialty camera shops. Things have progressed since then but even now places like Best Buy have very little M43 on display. By contrast I was in a Jessop's in London a few months ago and they had a wide selection of M43 cameras.

A large portion of consumers will make their purchase decision based on what they learn about in a store, and they cannot consider what they do not see.

One could argue that US retailers are simply responding to consumer preferences, but it doesn't change the fact that Panasonic and Olympus will need to be more aggressive in US retail channels for their M43 to become more mainstream here.