Kate

Looks like Brightkite with some of the features removed and Yahoo integration tacked on. Not that Brightkite broke completely new ground either, but Fire Eagle really looks like a knockoff.

He's simply making the point that even when your business can't capture a fraction of the total market that's worth discussing in numerical terms the numerator can still be quite noticeable. Your average small web company wouldn't mind having 100K paying users right now and they probably won't when 1M is less than 0.05% of net users. Reasoning about percentages and limits is relevant if your target user base is of the same scale as the total market or you're counting on a VC pitch based on winner takes all. It's not mandatory if all you care about is building a sustainable business: My local coffeehouse probably has a few hundred regular customers and their share of the worldwide coffee business is effectively 0%, but they're doing just fine financially.

Perhaps it's a cheap shot, but he apparently doesn't know what ISA stands for - it's glossed as "Industry Standard Architecture". I think you're off base on Apple's ability to port to a new (or old, for them) architecture and handle app translation on the fly. They've done it twice before with very good success and OS X has the infrastructure to make it as easy for them as it's likely to be for anyone.