For 12 years I worked in wholesale magazine distribution in the UK, the market dynamics of which are somewhat different to the US (- more magazines survive on newstrade sales alone than in the US, where news-stand sales are more often only a useful adjunct to subscriptions, due largely to the small geographic size of the UK, and publisher-funded sale-or-return).
1) Does this seem like a embarassment of riches to you?No. If the market can sustain six hair magazines (there are probably rather more than six available, but the ranging/merchandising decisions made by the retailer - i.e. how many of those available should they stock, which ones, and how should they display them - will have narrowed it down to what you saw), then clearly the public isn't embarassed by their wealth.
2) Who is reading these things? At a guess, women under 45 years old.
3) Will all these hair magazines have a detrimental affect on the follicly challenged amongst us?No. Magazines and other media can have insidious effects on certain people, but generally they are subsets of their target market. For excample, the use of very skinny models in fashion magazines (and the rest of the fashion media) does help to distort the body image of some young women (who are, after all, the target market for most fashion magazines).
However, bald men are not the target market for hair magazines, and rarely even see them (dollars to doughnuts all six magaines you saw have been around for years, but you've only just noticed them, and only because the grocery store you went to had them on display where you noticed them this time), so it's doubtful that they'll get enough exposure for their self-image to be influenced by them.
Certainly, 12 years in the magazine industry (dealing with hair magazines, among others) didn't affect me, detrimentaly or otherwise. Me, who occasionally posts on other boards under the moniker "ShinyScalp".
4) Have you ever purchased one of these mags?Good god no!
5) What, if anything, does this say about our society?That most women and some men like to spend money on styling their hair, so much so that it can sustain a whole industry producing magazines that allow them to think of new ways to do it even between visits to the salon.
And that bald men have little use for them. (Or perhaps there's a gap in the market for "Slaphead Monthly"? I can't see it being an especially riveting read myself, mind you.)
6) Are there any other magazine genres that strike you as being over produced? If so, which and why?Pornography. You think six magazines is overkill?

Plus, who needs the mags when they've got broadband *ahem*
Women's lifestyle/fashion. Ok, here I admit that when visiting friends' houses, dental surgery waiting rooms, etc. I really enjoy nosing through this. But surely every woman in the civilised world now knows how to get promoted while making a restaurant quality souffle and achieving multiple orgasm? And it strikes me as odd that their male equivalents spend so much paper agonising over how women think, etc., while women's magazines spend almost no time at all covering how men think. The assumption is, of course, that all women already *know* how men think and always have done. **Insert your favourite aphorism on the etymological origins of the word "assume" here**
Motoring & motorcyling. Ok, so at least half of men are thinking about their car or bike most of the time.
Caravanning (probably called "trailering" your side of the pond) - dull magazines for dull people to read up on their dull hobby.
Ultimately, though, this is about what you are interested in. MAgazines that cover stuff you like and are enthused by - can't get enough of 'em. Magazines that cover stuff that leaves you cold, or actively annoys you - shouldn't be any of 'em.
'Twas ever thus.