The first thing that everyone at my office noticed when I forwarded this link - they are only open from 10:00 AM to 6:00 PM EST? Hopefully that that's the first thing that's tweaked, otherwise anybody on the west coast who wants to notarize something after 3:00 PM is still faced with heading out of the office, plunking down $5 and getting their document stamped.
I can see this being very convenient for people who are located in rural locations, though I don't know how much business those people will generate.
Of course - the biggest challenge here will be price competition and a race to the bottom. At $5/notarization, it usually takes 3-4 minutes to get somebody's passport, ID, data, etc...
Watching the video - the one thing going for signnow is it will escrow your notarized document. Maybe the real play here isn't so much notarization as a business, but the brand development of signnow by offering peripheral services.