Dave (L) is an incredible guy. He's a musician, and a very big fan of Jazz. He's been working on a music composition program (Song Trellis) for as long as I can remember.
I learned a lot from Dave, not all of it related to developing software. You can, too, if you follow the link above. I highly recommend his article.
As for which "Dave" is "Big Dave"? Well, Dave L is no small guy. We had another Dave who worked on the Mac Word 5.0 project. He wasn't a little guy either, but Dave L still got the moniker "Bid Dave." I suppose one could say that Dave Winer is "big" in many ways, but Dave L will always be "Big Dave" to me.
Currently playing in iTunes: Famous Alto Break by Charlie Parker