#Freetheboards

There was a lot of this 'Free the Boards' stuff going on in Bristol earlier in the year, I thought it has fizzled out, but it looks like they are at it again.
The basic premise seems to be that they cover the adverts over with this light blue paper in order to liberate the billboards. I don't think I'd be very impressed if I was an advertiser. Also, could they not put something a bit prettier up there while they are at it?