I can be passionate about either strategy.
Losing a key player in preseason, especially a QB... is probably the most devastating thing a fan can go through. Before you've begun you're year is toast, unless Warner is in the wings.
At the same time... nothing substitutes for live action game situations to prepare a team for a season/game. I truly believe that. I hated sitting the starters almost completely at the end of last season.
I do not, however, think a full 4 games of full contact is necessary for season preparation.
BUT ALL THAT SAID... I have to believe this has been thoroughly analyzed by the NFL and each individual team. I wouldn't doubt if there are not some 'behind the scenes' agreements between coaches about who, when, etc. during these preseason games.