I'd think that even taking into account the phenomenon described in the article, it would be quite difficult for a new startup coming that late into the game to build enough traction to be a threat, barring any new and significant ideas.

This is also where IP comes in... can you reproduce someones product without violating their patents?

Most of the time, I reckon, yes.

Does feedburner even have patents?

Have you actually looked at patents? They are a cesspool of legalese and trolling for settlements.

Aren't you just conceeding the point? Patents are crafted like that precisely to prevent people from reproducing the work without violating them. Precise statements are easy to get around... fuzzy ideas and claims are much harder to circumnavigate.

Yes, but if this cesspool were a real barrier, nothing would ever get done! Ignore at first. You'll be too small to sue. When you start to get somewhere, you can attract those with the resources to defend you.