How can service providers ensure that PoE problems don't hamper 802.11n adoption?

There's not too much the service provider can do other than verifying that the Power over Ethernet switches they buy are compliant with 802.11n hotspots, which can require over 15 watts of power. Current Power over Ethernet switches can only handle a maximum of 12.95 watts.

Unless the customer is set to install Power over Ethernet right now, my suggestion is to hold off unless they have a really demanding network that needs that extra bandwidth and range. It's better to wait until Power over Ethernet technology is more developed. The IEEE Standards Association ratified the 802.3an standard that will let Power over Ethernet carry 56 watts, thus allowing service providers to support more demanding networking needs. You don't want to dip your hand in too early, or it can really bite you as a service provider later.