In case it helps anyone to extract any conclusions (from a micro point of view).
I have a single site that could fit the "mom's&pup's" definition (e-commerce and about 40 pages).
New domain (no previous history) and went online in March-09. I've done no advertising. I've submited it to about 40 free directories and it has about 10 natural IBL's. (completely white hat)
As I have no resourses for ads, I've gone for giving substantial information about the products, not just technical specs (the only mention of "buy" is on the alt buttons). Its architecture is basically in just 2 levels.
It ranks on first page for many 2-keywords, but since about Nov. more long tails have been appearing on my stats.
In previous months, when others where reporting loss of trafic or drops in ranks, my site was gaining some more traffic and gaining some positions in the ranks, although the increased trafic seems to follow a steady line of about 10º/15º (no big jumps).
I also had a big crawl in April, but saw no drops after (nor ranks or traffic), but more longtail kws like "How to..." or "What is best..." have been bringing trafic (nothing huge).
If this is happening for many micro sites, could this justify the loss of traffic for macro sites?