Wedding cake is almost always bad, but Sylvia Weinstocks cakes are always good; thats one reason that Weinstock, whose Tribeca shop produces the most sought-after wedding cakes in the land, is who she is. But there are other reasons too. We stopped in and tried to capture the Sylvia experience on video the other day. Is the pleasure of getting a cake from this woman one reason for the skyrocketing divorce rate in high society? We make no surmises.