Not including flash on a tablet seems like a mistake to me. It's one thing on a cell phone, but quite another on a device that will probably be positioned as a casual use computer.
There's a larger strategic issue here. HTML 5 is going to reduce a lot of the need for Flash and Flash in turn is going to be forced back into it's traditional market of providing streaming media solutions. In that role they are Apple biggest competitor both in format (Quicktime) and content (streaming media competing with iTunes)
By keeping Flash off the iPhone and the tablet Apple is taking their very high income audience and telling web site developers "Support us or risk losses in advertising". In doing that they're using the iPhone and the tablet to further the company as a whole. Something that might be worth losing a few sales in the short run