Li pointed out that current mesh protocols don't give nodes incentives to forward one another's packets. This isn't a major problem in academic, corporate or government settings where all the nodes can be assumed to have the same owner. But in open, heterogenous networks, each user will be tempted to "cheat" by modifying his own device to take advantage of other nodes' forwarding services without reciprocating. "It's still an open question whether we'll be able to solve this incentive problem," Li told Ars.
A related concern is security. Users should worry about the security implications of entrusting their packets to random strangers. Things would get even more dicey if routing protocols were enhanced to add monetary incentive schemes such as micropayments; in that case, security flaws in mesh networks could allow unscrupulous mesh participants to generate bogus traffic in order to siphon money away from their neighbors.
These are indeed serious problems that have to be solved before this approach to networking has a prayer of commercial success in anything but niche markets.