>One of our infrastructure on a client site includes a .NET Web Service which uses VFP and WWC for the data tier. Today, a top IT in regards to the management of that infrastructure says that this solution is not scalable. They said to us that a global .NET solution is scalable. How do we react to that?

Maybe he wants to sell you some .NET consulting services. "Not Scalable", like we haven't heard that before.:)

Doesn't that word mean whatever the user wants it to mean.

Tell him:
"Scale this!"