Fax is certainly an option as a distributed capture on-ramp.

Here's a white paper about the advantages of using fax server software with MFP devices as opposed to fax cards.

Click here to read an article on why fax is an attractive method of scanning documents.

Fax-over-IP (FoIP) is the latest rage in the fax industry. It follows on the heels of VoIP, but has some unique issues that possibly make it more attractive as a service than an internally run applicaiton. Check out this article by MyFax VP of marketing Steve Adams on the advantages of an FoIP service.