Did your previous patents bring you enough to make it worth your while ?
Personally I'm against all patents, especially software patents. If a competitor would come up with a copy of your service would you sue based on your belief that they must infringe your patent ? Would you consent to being sued in case it turns out you are infringing someone elses software patent ?
Don't you think the copyright on your software provides you with adequate protection ?
I understand there may be a financial incentive to do this, and there is the angle 'if I won't do it someone else may do it', but especially in the field of software I think that patents are best avoided. Personally I've given every so called patent holder the finger (there was that outfit that claimed I was infringing on their patent to send video over the internet, then another one that claimed I was infringing on a patent to rank video based on popularity and some more that I've forgotten about). In all of those cases the so called 'patent holder' (I think patent troll is more appropriate) called it a day when I refused to budge.