shrug ignore them and keep doing what they're doing? No need to worry about it until it becomes a problem.
And when it becomes a problem, they can make an injunction and shut you down having made you waste a lot of money and time?
If you don't build things covered by patents, you would quite literally never build anything - particularly in the software world, which is riddled with useless patents.
martythemaniak is right - build it first, worry about patents later.