Apple's iPad is a consumer device, first and foremost. (And it's a good one, at that.)But a few recent events have illustrated how the iPad could also potentially become an important device for business and enterprise users, as a lightweight, reliable, powerful -- and most important, easily programmable -- touchscreen tablet. And that could be a big opportunity for Apple. First, there's the restaurant check-in and queuing system we saw getting tested in San Francisco last month at the 21st Amendment Brewery restaurant. When you check in to the restaurant, the host puts your cellphone number into an iPad via...