So a thing that comes up a lot in working with data is the need for reconciliation, where you have two datasources and you need to match them up and see whether everything in one is in the other, and vice versa. (This is overall a part of the whole data quality issue.) So here I am, today, seeing what's out there - the answer is, unless you're buying SAP, very little (there is a Perl module, kind of, for doing table comparison) - and lo! the process of data reconciliation was patented in 1999 by Qwest; later, JPMorgan Chase inherited it and later sold it off.
Can you believe that? Can you honestly believe that somebody patented the very idea of finding records in one list and matching them with records in another list? This is the kind of nonsense up with which we really should not put.