First of all, MBay isn't "charging for drinks." What they've done is restrict the comp authority of bartenders, who no can no longer comp drinks to video poker players at their bars. As we wrote in the last Advisor: "The reason is supposedly linked to problems in verifying buy-ins on ticket-in ticket-out machines."
You can still get comped drinks at the bars, but they have to be approved by a floor supervisor. (Basic strategy: As soon as you sit down and load up a VP machine, call over the bartender and get the comped-drink process started.)
As far as we know, drinks are still comped to players at the machines on the casino floor with no supervisory interference needed.
As for this becoming a new trend, it's hard to say. This is only the second time a casino has attemped to limit drinks for VP play at bars in the past decade or so; MGM tried it awhile back and it lasted only a few weeks. Right now, we'd call it an experiment in trying to take away a policy -- an entitlement, even -- as entrenched as this one. Also, though we believe drinks for play is a generous comp, it's certainly in the casino's interest to ply players as full of booze as they can, which makes them reckless and takes them off their game with the first sip.
Of course, if this policy shows up at any other casino down the line, it could turn into a trend. Only time will tell.