The scuttlebutt here in Vegas is centering on 2 things:
1. Mayweather doesn't want the fight in March, the Pacquiao camp does (Pacquiao will be campaigning for a Philippines Senate seat after March). This is one tactic to delay the fight to the preferred first or second weekend in May.
2. This is a stall tactic by Mayweather to get more money. The contracts aren't signed yet, so this generates controversy, which generates more pressure for the promoters to get the deal done. The more pressure it generates, the more money Mayweather will get.
I do think the boxing public here in Vegas was surprised by Pacquiao's response and refusal of all testing. Could be a tactic by him to generate more controversy and buzz, which should lead to more money for him.
The bottom line is this, the fight WILL happen. There is about $80 million dollars on the table already for this fight, no way in hell either of them walk away from that once in a lifetime payday.