Massa can still, mathematically, win the title but it would take a very special set of circumstances. Thus Alonso doesn't have to worry about his team mate - indeed he can expect the team to start instructing Massa to be actively helpful. None of the other title contenders can expect that yet - although Vettel is pretty close because of his position in the team compared to Webber (not the publically nominated No.1 but he is the de facto No.1 at the moment).
I can see the two McLaren drivers finishing the season in worse positions than either might expect to with a "soft" team mate. That is the down side of having a policy of equal treatment between drivers. However, if one or other finds themselves massively ahead of the other one in a few races' time then I'd expect the team mate to publically state their support of the others title bid.