What's a "tour guard?"

Really, I have to agree with cur above. It's ALL part of the package!

And perhaps you can occasionally turn some of the pestering to your advantage. If you want to take photos of local people, in some places they expect money in return. Why not do that sometimes? Offer a bit of money and gesture with your camera showing that you want to photograph them. This may scare some off who don't want their picture taken, but that's a good result. The ones who agree to have their pics taken may provide you with some photos that you will prize later on (even though it may not seem so at the time).