So it’s the season of social commerce love – brands and social commerce platforms in all sorts of exotic combinations.

Hot on the heels of Gap’s promotional affair with Foursquare/Twitter/Facebook, the retail giant is getting it on with group-buy platform Groupon, where on August 19 you can/could buy a $50 voucher for $25.  We’re not sure if it plays nice with the above-mentioned extended ongoing 25% multi-platform promotion, but Gap is certainly playing the field in social commerce. Update – Mashable is reporting that the Gap promotion has broken all records on Groupon – by 5pm 300,000 Groupons had been sold – about 10/second.  That’s 3% of the total Groupons the fledgling social commerce platform has ever sold in it’s first 18 months…

And today, Target is hooking up with members-only private-shopping club Gilt (who had a recent summer affair with Starbucks), to launch its latest designer sale.  Members get early access to Target’s latest partnership with top designers (last year it was  Jean-Paul Gaultier, this year Gaby Basora (Tucker), John Derian and Mulberry.), offering catwalk and designer homeware labels at Main St prices. In return, Target will get extra word of mouth and editorial publicity – as the designer-ware talk zips through social networks…

Apart from the gossip value of these summertime trysts, what’s interesting from a social commerce perspective is that we’re seeing Groupon and Gilt emerging as mature social commerce platforms for big brands.