To thank its beloved customers, Bank of America, a major sponsorof the Giants , arranged for Buster Posey to make Thursday morning surprisevisits to two banks. A Facebook message - with no locations - said Giants tickets would be distributed,and he would pose and sign baseballs and paraphernalia. For me, theinvitation included a chance to chat with Posey. How to catch thecurveball isn't on my agenda, but with his wife's pregnancy, Ithought I might ask his views on natural childbirth. So, having been tipped off to location 1, I set out. OnThursday, Obama morning. The bus sat in traffic for 10 minutes onMarket Street around Sixth, and I fretted. But with cars on theright inching by, the driver wouldn't let me off between stops.Finally, an inspiration: "Are you a baseball fan?" Ye