Checking out all the pictures of the team celebrating last night I keep noticing that they're pouring crappy beer on each other instead of champagne in nearly all of the shots. Only the Natinals, signature move by the cheap ass Lerners.
Some MLB teams have deals with beer companies for this kind of stuff. The 2005 White Sox poured Miller Lite all over each other to celebrate winning the ALDS, and it was product placement for the TV audience.
If the Nationals are being paid to celebrate with beer, it makes sense that this is what you would see in pictures and on TV.
