In the login page for Web Data Entry it is possible to select a ODBC data source for data entry (Advanced options). Is there any recommendation by TIBCO to enter data in the common SEWSS enterprise DB, or in a separated DB, when the customer has a lot of Data Entry Setups in use?

Data Entry setups are stored in a meta database. Typically all data entry setups are in one meta database (the same meta database setup during installation of Statistica Enterprise).   However,  another meta databases can be setup and pointed to in the web data entry login screen:

It is not recommended to have the data entry setups on a separate meta database unless performance or the size of the samples per data entry setup is causing performance issues. 

The typical use is for users who have several environments with different meta databases for each, for example Development, Production, and Testing, environments.  If this is the case, users can add the DSNs to the System DSNs of the machine and then the ODBC Data Source will list all the available DSNs to point to.