We have been using Magento for 1-2 years and we routinely export the customer data in csv format so that we can market to them again.
However, we know that a lot of people check out as a "guest" and even though they enter all of their contact information including email, we are unable to extract it in any export.
The only way we have been able to get their data is manually going through the invoices and copy and pasting the ones that have "guest" or "not logged in" associated with their order.
Regardless of the method we would liek 2 things.
1) Extract all the data right now so we have a current Excel/csv database of all of our customers including "guests" and "not logged ins"
2) Give us instructions or tools on how to export all of them in the future.
13 freelancers are bidding on average $127 for this job
I can have this done in a few hours. I'll send you the first csv and i'll edit the core code to allow you to export guest emails with your regular csv customer export.