According to Fire and Ice, NBC has banned both the Rangers and the Devils from having viewing parties at their arenas for the remainder of their Conference Finals series. This Scrooge-like move was "ratings related" as they felt that fans showing up and watching the playoff games together might have a negative impact when the TV ratings are tallied. This amazingly also isn't the first time NBC has prevented teams from having such parties.
To put it simply, this move to ban team viewing parties is preposturously paranoid. Of the approximately 115,000,000 US television households only 25,000 are Nielsen households that have any effect on the reported TV ratings. So the chances of a substantial number of Nielsen households not tuning into channel 600 (or whatever silly high number OLN VS NBC Sports is) because they were at the stadium is minimal to say the least. Check out this video of Devils fans "packing" the Prudential Center for a viewing party for Game 2 of the Rangers series.
I've been to team viewing parties before. They can be a fun way to bond with your teams fans and build excitement in the city while being blasted with t-shirt cannons at timeouts. You also still get the pleasure of paying way too much money on concessions/parking and whatever else you could want in the arena. I'm sure this is money that the team and most importantly the workers that get to punch-in an extra night would really appreciate.
The NHL Playoffs have been excellent this year. Knowing how much Nielsen households apparently love awful reality shows over actual good TV it's not like they were going to tune in to NBC Sports en masse anyways. I'm a normally peaceful person, but if I ever run into one of the fossils that apparently is a Nielsen household I'd probably release years of nerdrage I've had building up in me and strike them down while cursing them for being the reason "Party Down" was cancelled.
I'm sure even with this move NBC Sports' ratings for the remainder of the Devils/Rangers series will still be substantial in the northeast and less so in the rest of the country. Basically, it's just a bullying move on the network's part.