Ask HN: Does a patent from a big company make a startup idea untenable?

Oh mighty and wise wizards of hackernews, I have a question I cannot answer. I seek a wizard of intellectual property strategy, for I have a question. (IP strategy is concerned w/ what actually happens, as opposed to the law, which is simply the law.)

I have a startup idea - I want to make an ad network for eBooks, and sign up publishers. I also want to make software to enable publishers to package special editions of their eBooks more easily, get metrics, etc. For the whole concept think Feedburner for eBooks.

Now, there are many eBook applications out there, and things have not consolidated yet, there are several large obvious companies with major interests in this space.

It seems that Amazon actually has a patent on advertising in eBooks or ereaders. You can see it here: http://gizmodo.com/5309001/amazon-patent-details-ad+supported-kindle-books

Does this make the startup not worth pursuing?

(It may be a bad idea for other reasons too. I guess we can workshop it a little bit on HN.)