"Is it a bad design idea to use a table as the data source?"

Go ahead and use a table as a data source, as long as you really need all (or most) of the fields from the table. If you insert a query between the form & table, you use more memory & the database grows slightly. Sounds trivial, until you get 100's of forms. If you only need a few fields from the table, the query is the better choice.