Do you really think so?
I don't really consider the problem to be any worse than I remember it being in the 70s or 80s where vandalism and asset stripping was equally as bad if not worse, and the internet didn't even exist in a public form then.
Sure there are undoubtedly people in our midst who have less than admirable aims, its been proven to be so many times. However they will still exist and do what they do whether they're here or not, the only difference is they wouldn't be able to call themselves urban explorers they would just be simple thieves/vandals as they always have been.
If nothing else I think the advent of the internet and almost universal access to transport has been a double edged sword.
Bear in mind this is only the rambling of an old git who started his explorations in a different world, the 1950s.