Do you mean that in each for, I would need to SetDataSource or something similar ?

There are two reasons:

1) In the old system, the tables were in separate databases, just a logical grouping more so than anything else, so this could be changed if its going to make the automatic switching of Production/Live or Company1/Company2/Company3 easier

2) The other reason was a cost saving issues. One of these Databses is a Data Warehosue type app where all the data from the other databases is sliced and diced and can end up to be quite large... up to 3/4 gigs. I may be wrong, but is'nt there a limit on Sql Express of 4 Gigs per database...so this was a way to keep the sizes manageable and not requiring the client to go out and having to buy full version of Sql Server