In many of my projects  including last one I need to user N-Tier architecture for my application. This is very good approach because you can centralize your business logic and have many type of clients (WWW, mobile devices) thanks WCF and REST technology. The other thing is that most of business solutions displays some data in tabular format knows as grids and grid has always one problem: number of records increasing in time. So we need to ask ourselves do we really need to display all the data together ...