Suing or threatening to sue people is definitely bad publicity and has borne minimum results, as this was aptly demonstrated in the long fight of the music industry against individual P2P? users. Still, the music industry kept fighting and fighting over a battle that was lost even before it began, one of the reasons being that there was no real possibility for recovering lost profits from the defendants. I think that RIAA was aware of that, and what they did had as its sole purpose to scare P2P? users, since the exponential increase of unauthorized copyrighted material on the net was killing the core of their business at an extremely rapid pace. Their response, I guess, was fueled by panic, not by reason. Perhaps the rapid increase in market share for OSS in the future may, in turn, lead Microsoft to panic and start suing big developers of OSS.

In the aforementioned analogy, however, there is one major difference between music file sharing and developing OSS. In the first case, a lawsuit has no other immediate impact but to the person being sued. In the case of OSS, a potential threat to an OSS developer means subsequent trouble for all the end users of the program developed by that developer. The effects of such lawsuits therefore are systemic, and even unpredictable, as they usually extend beyond the software industry, into the industries in which the end-users of OSS are active. So the question for Microsoft becomes a matter of figuring out how many enemies would such a lawsuit muster against Microsoft, and whether it is in a position to fight such a battle. Considering that OSS is currently being used by major players in sectors ranging from financial services through manufacturing and distribution to the public sector, it seems highly unlikely that Microsoft would like to fight in so many fronts. After all, many of these companies that use OSS may be Microsoft's shareholders or, at least, clients of Microsoft's shareholders.

As I read your comment I understand that, indeed, the troll threat that OSS is facing does not jeopardize OSS adoption by a wider user base; it is mainly a problem of increase of overall costs of OSS use by software users, as trolls take big or small bites at commercial OSS users, who, either because they are bullied through FUD or because they cannot afford a arduous and costly legal battle, decide to settle "amicably" with a troll. Logically however, since this technique did not work in the past, when the market share of OSS was smaller, it will not work a fortiori today, where the OSS user community has grown and established itself in all sectors of the economy. In this sense, people will not stop using OSS because OSS is constantly becoming better as it increases its share ("enough eyeballs" argument) and therefore it is becoming more important for them. It is a sort of a virtuous circle.

Since the 1990s, the term has been used to characterize a facet of Microsoft’s response to the open source movement, which has been implicitly acknowledged in the company’s internal “Halloween Documents”. The Halloween documents comprise a series of confidential Microsoft memoranda (drafted by Microsoft employees Vinod Valloppillil and Josh Cohen) on potential strategies relating to free software, open-source software, and to Linux in particular; and a series of responses to these memoranda. Both the leaked documents and the responses were published by Eric S. Raymond, an open source advocate and co-founder of the Open Source Initiative. Marked "Microsoft confidential", these documents identify open-source software, and in particular the Linux operating system, as a threat to Microsoft's dominance of the software industry, and suggest ways in which Microsoft could disrupt the progress of OSS. According to the Halloween Documents, OSS is identified as a “long-term credible” product and thus “FUD tactics cannot be used to combat it”. Still, over the following years, Microsoft has made various announcements regarding the potential dangers of developing or using OSS software, particularly with regard to the General Public License’s (GPL) “viral nature” which “_[...] poses a threat to the intellectual property of any organisation that derives its product from GPL source_”, and to the potential liability for users of Linux, since the latter software allegedly infringes 235 of Microsoft’s patents. This acknowledgment has been recently followed by relevant legal action taken by Microsoft against a company using Linux as the software platform for their products. The latter case was eventually settled out of court.

TomTom's decision to settle with Microsoft may serve to show that Microsoft patent enforcement agenda may not be obsolete yet. But in light of the foregoing findings regarding the importance of some OSS commercial users, this agenda is definitely undergoing a thorough review. In one strange twist, strategic litigation may have acquired a new meaning and goal: in the case of the music industry, strategic litigation aimed to cause the widest possible impact to the community of P2P? users. In the context of patent infringement, Microsoft's strategic litigation is probably aiming solely at maximizing profits from their IP portfolio, without stirring the waters of the ecosystem that includes developers, users, clients and investors who are directly or indirectly in favor of OSS. TomTom? seemed like a good target for Microsoft, being relatively deep-pocketed but also not a key or significant player in the market.

Controlling software's "means of production", i.e. programmers, can indeed be achieved through a number of ways, one of them being setting the rules (and consequently the limits) of what can be programmed under a given set of restrictions. Microsoft's attempt may be considered, I reckon, as a different sort of "walled garden", and as a predecessor to Apple's current attempt to indirectly control software production through its app-store. Of course, in an App-store environment, the extermination of third party unwanted code is implemented from day one, embedded in the systems architecture: There is no need to figure a strategy to embrace and extent.