HungryHobo's comment on /.:
1: I write some nice software and sell it.
2a: I make a little money, not enough to quit my day job.
2b: I don't make money, all I've lost is time.
1: I try to research previous patents, they're almost unreadable..... I have no money to hire a patent lawyer(barrier to entry one)... so I can't be certain if my idea has already been patented.
2a: I stop for fear of infringing on someones patent and being sued into the ground.(barrier to entry 2)
2b: I keep going and write my app... it might be infringing but I don't think it is....
3a: I make a little money.
3b: I make no money.
4: Someone sues me.
5a: It is infringing- well they pull out records that yes I did view their patent in the course of my research in step 1 and obviously stole their idea. They get tripple damages I lose my house. (barrier to entry 3)
5b: It is not infringing - so what. I don't have the money for a good lawyer, they win I lose my house.(barrier to entry 4)
5c: It is not infringing - by some miracle I win.... I'm still left with a pile of legal bills and I lose my house.(barrier to entry 5)
In theory the patent system could help me by letting me be just like the guys who sue in the above but I don't have the thousands of dollars it takes to get a patent through nor the time.