I think bridge example is rather good, except that you should note that bridge itself is physical and technically everyone can build one, therefore if bridge owner wants too much money for going over it you can build your owns.

Bad things happen when building a "bridge" becomes really easy and cheap then he realizes that everyone can build their own bridge, so he gets a patent for "bridge", so no one can build one and he can keep his profit. There is cases where such bridge was in fact something really smart and worth to be protected, then such patent does in fact protects his time and effort he put into inventing it.
However imagine a case that nobody ever before saw a river and needed a bridge, he was the first to come to a river and crossed it buy just dropping a tree over it - then he comes home and gets a patent for a "bridge" = everything put over a river to cross it. Invention is trivial, every thinking man would come up with this, but sine he now owns a patent for it noone else besides him can now build bridges EVER without buying his rights for over 9000.

Same happens in software market and it does slow down or even make impossible many things that might have come to this world without all this patent crap.

IP laws should be changed, but the reality is noone knows how to do this in a fair way, therefore we are stuck with this crap. Logic tells you every man shall be rewarded proportionally to the efforts they've put into creation, but while it is relatively easy to do calculate values of physical goods it is close to impossible to achieve the same with intellectual property, even worse when they come combined in one physical product.