I'm an undergrad, and haven't moved very far into my courses in Physics. As I look around the internet and books to gain information about string theory, it seems to me there is a much more heated debate about the acceptance of it, compared to older theories such as Quantum or Relativity.
What is the primary reason for the - seemingly - rather widespread nonacceptance of it?
I've heard it described that String Theory is in the stage now that the atomic structure had in the late 19th to early 20th centuries; there wasn't enough experimental evidence or foundational knowledge to know for sure that atoms [or in this case - strings] existed.