I teach kids (elementary age) for a living and we decorated our classroom last month so I suggested we buy a pack of blutack to put up all the posters with their school projects. They had lovely drawings and projects to put up, so I wanted to buy something that wouldn't stick to them forever so that they could take them back home when they wanted to.
We only used up one and a half of the packs and managed to stick at least 15 posters, drawings, cut-outs etc. to the walls and our new classroom looks amazing! We were all excited by the final result (and so was the headmaster, on being shown that they didn't leave any marks on the wall).
I would recommend blutack for anyone who wants to put up things and decorate walls without fearing that removing them will take away chips of whatever you used to paint your walls.
Also, the best thing about Blutack, besides the fact that it really manages to keep things in place, is that you can reuse it a couple of times and you don't really need big bits of it to keep your posters, papers, cards you name it, in place!
And 12 packs for this price! Oh boy...That was a great deal!