Wood-Grilled Oysters in Chipotle Vinaigrette

"It used to be that you could buy and eat oysters only in months with an "R" in them. That's because during the summer months of spawning, wild oysters develop an "off" flavor. Transporting oysters in hot weather, before the days of refrigerated trucks, was also problematic. Today, about 80 percent of oysters are farm-raised in submerged nets, dining on plankton in carefully controlled marine environments. They spawn at different times during the year, so there's always a variety available that's good to eat. When ready, they're harvested and shipped by air to seafood markets. If you're not comfortable shucking oysters at home, have the fishmonger shuck them for you and ask him or her to give you a half shell for each oyster. In this recipe, you'll get smoky flavor from two sources: the wood-grilling technique and the chipotle chile in the vinaigrette...."