I've spent a lot of perfectly wonderful hot days kicking around in my float tube dragging a streamer or large nymph behind me on a sink tip line. It's saved a lot of days for me when other methods have failed and the fish are deep and/or scattered. But is it flyfishing? Well, I've found the method detailed in many books on flyfishing and in a few dvd's I know of (none of them titled "Flyfishing and other methods") and all of them treat it as a valid method. Of course one of those books also treats plastic worms as a valid fly as well, but I choose to not let that invalidate the source . At the end of the day it depends on these things:
Is it legal where you are?
Does it work?
Are you enjoying yourself?
Would you admit to your mother that you are doing it?
Basicly, if you are having fun, catching fish, and staying legal, then it doesn't matter whose definition of flyfishing it fits as long as it fits your own.
If it swims and eats, it'll eat a fly.