Pat Burrell was always on the bubble of whether or not he would be offered arbitration, since the Phillies want no part of paying him more than the $14.25 million that he earned last season, even if it's just for one season.
Since the Phillies declined arbitration offers to Moyer and Burrell, if those players sign elsewhere, the Phillies will not receive any compensation for losing them. Had they offered arbitration, the Phillies would have been in line for two additional draft picks if the players signed with another team.
The fact that the Phillies didn't offer arbitration doesn't mean that they aren't interested in re-signing either player. They can continue to negotiate with both players. It's unlikely that they'll re-sign Burrell, but they remain interested in Moyer, who led their pitching staff in wins last season. Both players have said that they would like to re-sign with the Phillies, but both are also seeking multi-year contracts and may want more money than the Phillies are prepared to offer.
The Phillies have shown interest in two other Type-A pitchers, Derek Lowe and A.J. Burnett, and both were offered arbitration by their respective teams. That means that the Phillies would lose their first round pick if they were to sign either pitcher. Other Type-A players that the Phillies had an interest in - pitcher Juan Cruz and outfielder Raul Ibanez - were also offered arbitration.