Patent trolling = A company that purchases a patent, often from a
bankrupt firm, and then sues another company by claiming that one of
its products infringes on the purchased patent..
(in other words, getting a patent on something without manufacturing
it and then waiting for another to come up with the idea and use it in
an invention)

Question:
1. Doesn't a patent need to be reduced to practice in ordered to be
issued (how can someone get a patent on just the idea itself?)

It is not necessary to actually demonstrate an idea to get a patent on
it. In patent parlance, the filing of the patent is considered a
"constructive reduction to practice". It is merely necessary that your
patent filing be adequate to "teach" someone with ordinary "skill in
the art" to build the invention. I would guess that most issued
patents are for inventions that have never been reduced to practice in
the ordinary sense of the term.