I have an idea for a courier service, which I'm not sure is at all
practical. But then since I'm not a tech I don't know. Here's the
idea --

Offering a service where a courier comes with some sort of laptop,
some sort of portable machine which can hold massive amounts of data.
It would be set up to easily transfer from most platforms by the most
common connections.

The idea being that for the customer to transfer 'huge amounts of
data' (I'm not sure how much) over the net they'd have to have access
to an extremely high speed connection to do it quickly. Burning CDs
or DVDs would take too long. They wouldn't have removable drives that
big. So the only way to get it from A to B (which are within 20 miles
of eachother) is to hire our courier with his dream machine, download
all the data, so he can go to B. The standard delivery time for
couriers in a metro area is usually 2 hours. I'm hoping some types of
data still take overnight or longer to send.

Is this at all a plausible concept? and if so, how long until it
won't be anymore?

I got this idea because, working as a courier in Seattle, I've pretty
regularly shipped CD-ROMs over to Microsoft. Most of the time it's
because some dept. like Legal or Marketing wanted a "hard copy" of
some data (!?). But then on the other hand, we take videotapes to TV
stations and ad agencies on a regular basis..