Thats only the start...
Fighting against someone infringing your patents is a tiny part of the problem for small firms.
The initial problem is it cost real money to create the patents in the first place. Its not difficult to rack up legal bills of £5k-£10k per patent. If you can't afford to do that then you can fall foul of someone a few years later creating a patent for something you've already developed. Then you've got the nightmare situation of demonstrating prior art.
Which brings me to my next point. Large companies throwing often bogus patents at anyone that comes close to the solution. As a small company its hard to defend although the larger companies tend to prefer to pick on other large players.
And finally, patents can be a major hindrance to raising venture capital. VC want to say patents but not only that , they want to see that your offering isnt infringing on other patents. Patent checks can also be an extremely expensive activity if you intend someone to provide an "Opinion" that ther are no infringements.
Then there are those dormant patents that are waiting to trap companies. The idea has not been implemented, the patent is vague and all the patents have done is hamstrung anyone that is actually trying to produce something for real.
I understand the need for patents on things like drugs where the cost of research and then drug approval necessitates your effort is protected. But there isnt a place for software patents, they hinder innovation rather than promote it.