maybe he had a toothache that day~~
i would think this is merely an example, and wasnt stating this is your only options. niche environments are devised based on the following of that specific entity, i think HL is starting a social network for "Proctologists", oh wait a minute, that was just for asses, not doctors of asses :)
at any rate, i think you may be reading more into the post than what was initially intended, but a social network for dentists is viable, not so much from just the day to day grind of pulling and filling teeth, but from new technology and resources. so the network would involve more than 'dentists' per se' but that is where you take your niche.
i have seen a wide variety of niche environments, and those are the ones i would tend to say have performed the best. trying to launch something globally is extremely difficult, both time consuming and expensive.
when developing for a niche environment, then you bring with you your knowledge of that environment, which if done correctly makes it more appealing to others of the same interest.
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