The 49ers can't trade him until March. If he does not sign with them he is worth nothing until then. That probably more than anything else explains the tampering charges. It's their only way out. Come March both the 49ers and Crabtree are screwed unless a trade can be engineered. The 49ers are particularly screwed because they get no compensation for the pick. BTW, it was not too long ago that it looked like the Jets would lose Revis after trading up to pick him. Their compromise in the end was to overpay him (for the 14 slot) for a 6 year contract.
How would it even be possible for the Jets to guarantee him money if he reenters the draft when they can't even guarantee that they'd be the team who drafts him?
Casserly was just saying on CBS that there is no proof at all that the Jets tampered. They never spoke with his agent or him prior to talking to SF.