The San Francisco 49ers cannot trade Alex Smith before March 12, but with word coming that a deal could be lined up, let's consider the possibilities.First, rules do allow teams to talk about trades and even agree to them informally before the trading period begins. So, it's possible the 49ers have done that during the NFL scouting combine. But the NFL trading period remains 16 days away. Teams cannot enter into binding agreements until then. We shouldn't get too worked up about potential trades until the 49ers and another team say they've reached agreement.