Actually, the reason it's not uncommon has to do with the sheer number of devices that use the 2.4 GHz range (not just other routers, but cordless phones, especially those that channel/frequency-hop, such as DECT) are a big reason why range shrinkage is an issue (not just with draft-N, but even g). It's why dual-band N adapters *and* routers are the only real solution to come close to taking advantage of all of N's advantages.
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