I'm not talking about parsing. It's a mess in it's own right of course (encoding, line terminators, etc as others mentioned).

I'm talking about the actual conversion from tabular data to relational. Most of the applications I've worked on had this in one form or another.

So you end up with users downloading an export of their data in CSV, editing it in Excel in various ways, and then reimporting it in the application.

Every company I worked for, this kind of feature was always in the top 3 in term of support load.