The sweet spot in business is when supply and demand are in equilibrium. Customers buy all they want; you sell all you got. This morning I noticed a perfect example of this in Google's Gmail.

Google markets Gmail through referrals. Current users can invite others to sign up for the free service. Early users were allotted ten invitations. After that, the invitation button disappeared from the screen.

Google must have caught up with demand, for these two links appeared on my screen this morning:





I assume these will appear whenever Google's ready to take on more customers.

Most messages I receive are less useful. What are these messages suggesting I do?





Here's a real show stopper. Maybe I should say "sale stopper." Barnes and Noble invited me to an online sale. When I try to place an order, I receive this somewhat geeky message:



Now what? I do have cookies enabled. Do you think they'll notice the problem before they see that online revenues are dwindling?