I agree with author's observation. My personal open-source projects are developed 95% by me, and sometimes overhead of collaboration (documentation, discussions) outweighed the contributions I've got (small patches that I had to refactor anyway).

However, this should not be interpreted as a reason to drop free software or that closed/for-profit software would fare any better. I don't think that the "long tail" of projects in sourceforge graveyard would attract enough commercial interest to fund several developers.