Chances are they obtained about 500 patents of similar reach per year. This is an arms race, with companies aiming to be able to countersue any patent infringement with hundreds of patent infringements the other way.
You're completely correct. Every big software company encourages their developers to apply for patents on everything they can think of, using cash bonuses and recognition. It's absolutely an arms race, because any company that didn't do this would be standing naked if a patent troll decided to sue. It really demonstrates the ridiculousness of the patent system and how far away it is from the original intentions (even assuming those original intentions are worthwhile, which is dubious).
Patent trolls don't produce anything that can infringe on a patent, so having a patent portfolio does nothing to protect against them.
A patent portfolio helps when a competitor claims their patent is being infringed. A company with a large patent portfolio can cross-license patents and avoid a lawsuit.
