The line between patentable and not patentable inventions is very fuzzy, and always seems to drift toward allowing a little more each year.
That hasn't been true for several years, and the PTO has been very tough on software patents since the Supreme Court decided Alice v. CLS. The PTO is currently rejecting applications that fail the "machine or transformation of matter" test, although sometimes they can be argued out of a rejection. The Alice decision is rather unclear, which annoys everybody.
The "patent troll" problem isn't that big. The EFF's data indicate that almost all the bulk infringement claims come from three lawyers in the Eastern District of Texas.