It seems to me that a petition -- or an open letter published (for example) on LQ -- might be a good idea if its well written. Keeping in mind the cliche "You will gather more bees with honey than with vinegar" is just the start of crafting something that is well written. What follows are ideas that I would expect to find in a well written, professional document (petition or letter). I'm posting them because the referenced letter is anything but professional and lacks any persuasive content, IMO.
Persuasive comment can include (among other things) the names of vendors that have recently changed their policy. If I recall the history about nVidia correctly, nVidia didn't support LInux at all but eventually came out with driver(s), albeit as binary files. IBM's decision to move a number of their patents into the Open Source community might also be persuasive. At the very least, making mention of the work being done on SourceForge seems like a good idea, to me. Some might say omitting a reference to SourceForge -- all the help that can be made available to assist driver development -- is even a little shortsighted.
A company too small to compete with HP (as an example of one company that has made great strides in printer driver development through SourceForge) may not have much to gain. And this is the bottom line. For a company to undertake a task that has a clear cost to it but does not have a clear return, they may need help figuring out the latter.