The National did similar Facebook/twitter spammery, especially about shows that weren't selling well. Also would do similar things hyping the announcement of upcoming shows (12 hours to the announcement... 9 hours to the announcement!, etc).
You know what I did? I replied to everyone of them with a comment about Foghat. If they announced they'd be announcing a concert soon, I'd go "Lord please let it be Foghat!" If they said tonites show is going to be awesome, I'd ask if Foghat was playing. If they wanted to know my favorite underselling bands song, I'd tell them it was Foghat's fool for the city. Etc. other people thought it was funny and started doing it too. After a few months, they cut way way back on the number of idiotic posts they made. I guess what I'm advising is spam the spammers, they'll get the message.