Well yes, there's a strong case for saying those are intrusive and people mostly tolerate them (but for lots of obvious reasons that can't apply to offerings at megalithic sites).
The other big thing about church bells and mosque calls is that they aren't imposed on the rest of society 24/7, which offerings left at sites are. This is my bacon sandwich point. If offerers came back in half a day and removed the stuff it would at least show a bit of respect to other visitors and people would be a lot more tolerant towards them no doubt. But just going home and leaving whatever they've left to annoy, detract or biodegrade smellily until people with more respect for the site and their fellow visitors remove them (AND get larupped for doing it!) is just a teeny bit naughty. ;)
Everyone seemed very touched and happy about the story of the carved pebble left in memory of a relative but what if EVERYONE did that? You wouldn't be able to get anywhere near the bloody place and then it would be considered tat and moved. What if you cant afford a nice carved pebble but the passed relative loved pottery cows (I'm sorry to keep coming back to the cow, I actually think its a bloody stupid thing to leave but thats not the point)! It shouldnt be any less important because we (the observer) think its less tasteful, it could be just as meaningful.
