I'm of the opinion they should only be in appropriate places - ie for navigation, especially on routes where going a bit off them could be fatal, or cause a serious injury.
I was deeply disappointed to see a 'memorial' on Stuchd an Lochain this year, complete with plastic flowers.
I appreciate that people like the idea of a memorial to someone they've lost, but I just don't think that's appropriate - especially not with plastic flowers.
There's a beautiful memorial in Glen Etive, beside the Allt Mheuran [Ben Starav/Glas Bheinn Mhor etc] tucked in against the trees.
I assume permission was obtained for it, but it's very moving. I don't think anyone could object to something of that kind.