It's true that the vast majority of free or open source fonts out there are garbage.
I would say cost would be more of an issue then developmental model (as both developmental models can cost the end user). If someone is doing it for free (especially if that also includes commercial use), there may not have been as much time to handle the nuances that really make a good commercial font. Such as these:
Some of the free fonts are so poorly constructed even turning them into outlines doesn't work. Not to mention kerning pair issues, leading, tracking etc...it runs the gamut.
I would also add in the availability of alternates as well don't seem to make it into the free fonts.
Google fonts (which is also open source if I recall correctly) and Font Squirrel are resources that I like. For Google fonts (if I'm using it for development) also work because they can be linked and not statically used as well (I do browser based games as well), so that is a nicety with that resource as well. Not very handy in this instance, just another nicety of that service that I like.
I highly caution using DaFont, even thought that is the most often used one or at least cited. Especially in the business use world. A lot of people don't realize (and this was already posted above) is that commercial use is usually not allowed (I actually rarely see commercial use also permitted without having to purchase a license). But more importantly, you have, a lot of the time, concerns that rjsigns mentioned.
I would also suggest evaluating on a case by case basis as not all free fonts are bad, the odds of it being so, quite a bit higher, but there are some diamonds in the rough out there.
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