I don't believe there exists a technology company in the world that doesn't infringe on patents (mostly unintentionally). I think if most of them really looked they'd find thousands patents they are infringing.
Most users here are saying that "ethically" MS is doing wrong. This is not an ethical issue, it's a legal one (MS isn't the only one, recently Apple, Nokia, etc). The problem of patents it's been around for decades, or at least years, why haven't anyone fixed it. America is a democracy, right? Now go and change the law, if you can.
Or, wait for a replacement of the current patent system, I think it's only a matter of years, now.
EDIT: Of the 5 patents I was talking about, none of them use the invention on an actual product.
EDIT2: clarified 2nd par.
The problem is, the system is set up in such a way that it's impossible for a small company to stay legal. Even if you grew into a medium sized company, and you managed to spend the time required to research all the patents you're infringing on, the licensing costs for all those patents would be greater than all the money your company will make over its entire lifetime. Because you now know about all the patents, even the silly ones, and you can't actually afford to challenge all of them, so you just have to license them.
That is what would happen if a small / medium company did its best to stay legal when it comes to patents. It's absurd.