Groupon, Foursquare, Scoutmob and Living Social are among a growing number of social media services that market health care goods and services.  Groupon (i.e. groups that get email coupons), for example, signs up subscribers who receive daily emails of coupons for discounts on, say, eyewear, vitamins, teeth whitening and hair removal.  The coupon only lasts for 24 hours, which encourages subscribers to buy on-line from sellers who pay a small commission to Groupon.  While most customers are young adults, this idea should appeal to elders and others who purchase wellness supplies.            MORE