With BSD-style licenses, everyone is also on an equal footing, except that now users have no guarantees that the software they use will be maintained as free software. At any point, a treacherous developer or company could scoop up the talent from the community and make a maintained fork of the project proprietary. The original project dies because of lack of talent and now free software has helped expand the reach of proprietary software.
Note that even with copyright assignments, there are some good ones. The FSFs (optional for projects) copyright assignment has specific wording that guarantees they will always keep the code free (and even go further to state that it will always be copyleft and in keeping with their well-documented philosophy). If I had a single foundation I had to pick to assign my copyright to, it would be the FSF.