It's not so much that they know the format... they are the format. Joel Spolsky (who used to work on Excel and now runs Fog Creek) talks about the issue here:

It's not so much that they know the format... they are the format. Joel Spolsky (who used to work on Excel and now runs Fog Creek) talks about the issue here: http://www.joelonsoftware.com/items/2008/02/19.html http://www.joelonsoftware.com/items/2008/02/19.html