This post is instigated by, but not in support of, the recent news that Yahoo is approaching Facebook about licensing patents they believe the social network has been infringing. The other disclaimer is that I personally believe the patent system, especially software patents, is in need of major overhaul and have been on the defendant's side of "patent troll" suits (which waste time and money even in victory). Listen to "When Patents Attack" from NPR if you want more info.
That said, two questions given the reality of today's legal system and tech innovation:
a) I still hear venture investors asking startups about IP - not just to make sure their potential investments are in the clear, but also to see what new technology the company has patented for purposes of protection and value creation. If we as technologists are dismayed by patent warfare, are we not complicit in these actions by continuing to play the game of "oh, these are for defensive purposes only."
b) Given a very competitive and fast-changing innovation environment, is there ever a time when it's right to use patents in an aggressive fashion against competitors (either as a licensing revenue stream or to block their entry into markets). I assume lots and lots of licensing dollars change hands every year in a perfectly hospitable fashion.