There are some interesting legal barriers to overcome in some of those cases.

In my country, faxes are legally recognized as evidence, but email isn't, so there's a strong incentive to fax documents.

A law recognizing electronic signatures might help things, but it's still pretty cumbersome.

I tried to build a solution for "escribanos" - the U.S. approximate equivalent is notaries, but they're specialized lawyers actually - and the legal hurdles proved impossible to overcome.

Stuff that is being done with fax machines out of ignorance would be a better place to start, but there you have to face conservatism (an admittedly easier barrier than legal obstacles).

Add Excel spreadsheets and Access databases to that list. Best thing, someone else has already proven their is a need for the system and a working solution!

That's good advice. In fact, this HN discussion has a "ridiculous" (in a good sense) amount of good advice.

The only problem is it's a lot easier to post, comment, kibitz, criticize than to actually do. It's nice to read the good advice here, but at the end of the day it's still necessary to do something useful in a startup. This isn't a criticism of your post, it's a general observation.