Yawn... First of all it's not PG's patent. Its Yahoo's. Second, if anyone ever goes after you on a software patent, celebrate! It means you are a success. It means you have deep enough pockets to be considered worth the trouble. Third, as much as software patents are a joke, see them for what they are: A little side show for the lawyers and MBAs to leach off the big boys and feel like they are holding important cards…
Patents may be a joke to hackers but they aren't to the investors who fund them. Of course if you don't need investors for what you're doing in order to be successful then more power to you.
Just don't worry about stepping on the other guy's patents. They are just paper really.
And as we know in this economy there is a lot of phony paper out there that people just want to call valuable/meaningful.