Open Source Silver Bullet
Recently Jörg Siever made a very interesting keynote speech at Eclipse Summit Europe about why VCs like open source companies. Even if you're not involved with venture funding, I still recommend this presentation for understanding open source business models. One of the comments he made (about open sourcing unpopular applications) reminded me of an open source antipattern I've seen a number of times.
In brief, open source is not a silver bullet for software product development. In addition the productivity issues that Brooks discussed, open source does not absolve companies from the requirement of providing valuable products and services. Simply producing open source software does not mean that money from adoring users will flood in. This might seem obvious, but I assure you it is not in many cases. Rather, a very common mistake starts from wishful thinking and ends in disappointment when open source involvement does not automatically translate into product sales.
Open source is a method of production, one which of course has advantages and disadvantages. For me the most intriguing aspect of open source is that the full potential of its advantages is only now beginning to be understood and leveraged. And, yes, there are real disadvantages that need to be understood and accepted; otherwise unrealistic expectations will certainly be the source of later frustration.