When you are providing database publishing services to your customers, you will often need to use their existing databases somewhere in your workflows. In many cases this will consist of product databases (especially for database publishing workflows), and in other cases it will be employee or office databases (for example for web2print applications). Regardless of the type of data, you've got a lot of tools to make the connections happen.
Direct interfacing to the customer database
In reality, this isn't implemented often. Your own servers are in a different network location than your customer's databases. And even if you have access, many database administrators won't be very happy to give you access to their systems directly. But if it's neccessary, you can use ODBC, OLEDB, or any other type of connection available to .NET. Which pretty much includes anything you'll ever need.
Importing data files
Much more often, you will be presented with data files for import. Tab delimited text files, csv files, excel files, and so on. Most of these can actually be imported without the need for scripting. Even when it is necessary, the scripting is usually limited to transforming certain values. For example: you get full telephone numbers without separators from the source database, but you need them with periods in between for the business cards.
Complex imports
In a few cases, you might be presented with very complex imports from the data source, with hardly any formating done. Dimensions, prices, and all other information might be available, but is delivered in an XML format without any formatting. If the product code start with "2", you'll need to build dimensions as "w x h". If it starts with "3", it has to be "w x h x d". And so on. Obviously this type of import is a lot more complex, but by separating the hard part (the scripting) from the easy part (the configuration), you can always get it under control as well.
Synchronization
And once an import script has been written, you can keep on using it. This way, synchronization of the data becomes possible. Update a few marketing fields in the FLO Suite database, and import the technical information (or addresses, contact information, ...) on a periodical basis.