Why "No Commerce" clauses are a bad idea

tl;dr Sticks and stones may break my bones but commercial use of my open source code may never hurt me.

Some excerpts from MAME legal information.

Q. Can I include MAME with my product?
A. No. MAME is not licensed for commercial use. Using MAME as a "freebie" or including it at "no cost" with your product still constitutes commerical usage and is forbidden by the license.

Q. Can I put an arcade cabinet running MAME in a public location?
A. No. This this a commercial use of MAME and is prohibited by the license. Even if you don't charge money, putting a machine in a public location is "operating" an arcade machine and falls under commercial rules in most locations.

Q. Can my non-profit use MAME or an arcade cabinet running MAME to help raise money?
A. No, sorry. Even for the most worthwhile cause, this still is a commercial use of MAME and is prohibited by the license.

Q. If I obtain a license from an original manufacturer to distribute the ROMs can I use MAME to run them?
A. Generally, no, because it constitutes a commercial use of MAME. However, we have in the past made a couple of exceptions for this particular case. We will not consider making any further exceptions without proof that such a license has already been obtained.

Q. Can I use a PC running MAME to replace a real arcade PCB?
A. In order to do this you would have to use a copy of the original ROMs, which would require obtaining permission from the original manufacturer. Once you had permission from them, if it was used for non-commercial purposes, then you would not technically be violating the MAME license. However we still do not explicitly give permission to use MAME in this way because of the possibility of the game being sold sometime later, which would constitute commercial use of MAME. If you sell your game later you must sell it without MAME included.

Q. Can I ask for donations for the work I did on my port of MAME to platform X?
A. No. You would be earning money from the MAME trademark and copyrights, and that would be a commercial use, which is prohibited by the license. It is our wish that MAME remain free.

Some more thoughts on why this is a bad idea:

PS: Just for those that don't get it: No, I'm not saying it's okay to commercially exploit someone else's work without their permission. But "no commerce" clauses don't help.