I'm talking about marketing more in the sense of "finding out what people are doing with your stuff, and moving your product in a direction that helps them" than "SELL! SELL! SELL!", which you really can't do with open source in any case.

The embedded vs batteries included example is a pretty good example of that: Tcl is neither small and limited/self-contained like Lua, nor does it ship with a bunch of stuff out of the box. So it satisfies no one.