There are always instances where being able to transfer that information would be incredibly helpful...and whether you allow one of your client's to do so is entirely in your control so I am not sure why this is a problem.  You can tell a client you can't or it is against your firm's policy if you don't want it to happen.  In my circumstance, I was the client and my tax preparer wanted to get rid of me because my taxes were becoming too complicated for her.  She hated my k-1's and in fact, did them incorrectly.  If I could have used that data to transfer from Pro-series to Turbo Tax, it would have saved me over a week of time (again -- my preparer wanted me to go because it was too hard).  Instead, in order to amend my return, I first had to recreate whatever she input incorrectly by trial, error and guessing.  Even with most of the worksheets, IT WAS SUCH A WASTE OF TIME AND INCREDIBLY FRUSTRATING!  She wanted to transfer the file and couldn't.  My foot was the only one shot.  If you do a good job for your clients, save them money then you have knowledge that is incredibly useful to them.  Transferring data doesn't replace the knowledge you have so you shouldn't feel threatened or feel you are shooting yourself in the foot.  Charge them for the data if you really need to -- but helping clients should be the priority.  If they are going to leave to do their taxes on their own, they will.  Most won't because they are afraid of taxes.