The mainstream don’t even use or understand RSS, but us techies have moved on to Twitter and FriendFeed.
Very true. While it's great to see all those new Web 2.0 ideas, innovations and technologies coming up every day, we (the Web 2.0 community) also have to avoid creating lots of products which no one else except ourselves is going to use any time soon.
If your startup's plan is to acquire millions of customers over the next few years (which is likely if you want to make money by selling ads), do a reality check and explain your idea to some "real" people among your friends and family.
Also read Josh Kopelman's great article about the same topic.