This is an interesting discussion thread. I thought I'd contribute my experiences from both a personal and producer side.
On a personal level, none of my family or friends know. I intend to keep it that way. As for romantic relationships, I'm still single, and never been successful in dates to the point of being couple. So obviously I've never told my dates about this side of me, because we never get to the point of being couple. Perhaps I am too choosy (physical appearance and especially quality of long hair matters a lot), lack the tact, or just plain unlucky. Who knows? But those are all long stories on their own...
But as a producer, I do have a larger hurdle to pass compared to others who are just "consumers". I not only have a "thing" for hair; I actually actively produce videos for the community! If I ever have a partner, it would be hard enough to explain to her about my "thing", but if she knows about my clandestine production, it's a whole other level to deal with! Eventually, it'll have to come down to choosing her or continuing production. It's wishful thinking to find someone open, shares the interest, and supports producing this "stuff".
On the producer experience, I strive to maintain transparency, so I use my real identity when dealing with hair models. The response is quite varied on a personal level, and also culturally. When I started, I was based in Australia. Being a Western country, even though people there are more liberal-minded, there is a major barrier to overcome which money cannot always buy; reputation. Many models are reluctant to do "these sort of things" because of fear of their reputation being ruined if they appear on "dodgy" sites. In a first world country, money is not enough of a factor alone to encourage people to model. Pride and reputation are often stronger factors than money.
Many of the models were surprised when they find out that hair fetishism is even a thing. Here's something interesting. I've had semi-professional models who are open to doing artistic nude / implied nude photographic shoots, but will not model for a long hair play video for sale (which is implied fetish, even though I never explicitly use the F word when advertising and communicating with models). They rather be seen nude for "artistic" reasons than appear on a fetish site fully clothed modelling just hair. Go figure.
But somehow fortunately, I could find models who were willing to model for my production in the early stages. For long hair play videos, the first few batch were made with models whom I have had worked with for other photographic projects; so there is already trust earned. For haircut models, they were from people struggling financially, so as long as they got paid, they didn't really care too much. Getting the first batch of products is the most difficult bit, because I had no prior examples to show for. Once the first batch is there, it is easier to advertise for models, since they have a tangible website to see for themselves what the production is about. It's a rolling snowball effect.
Here lies the great irony. My own family and friends know nothing of this side of me, but strangers do. Well, since I am a photographer, it is not unusual for them to see me carry so much equipment in my car, and go out for shoots. When they ask what I am doing, I just say I'm going for a shoot. Technically not lying. I also do "normal" portrait shoots which has nothing to do with hair at all, and other kinds of photography out of interest; so it's easy to conceal my hair video production business among these other activities.
Currently, I am producing in Bosnia & Herzegovina. Being an Eastern Baltic European country, the mindset is completely different. People are conservative and find our Western indulgences strange. But, money is a huge pulling factor there. The country is poor, and half the people are without jobs. They care less about reputation, because the videos appear on an English / Western site; highly unlikely to be found out by their family / friends / future employers. So as long as they get paid, they will do it.
The bonus as well is that being a conservative country less exposed to Westernism. Beauty is a subjective thing of course, but there are some aspects that are objectively quantifiable. From my travels, I have found that Eastern European women are of much better quality, physically wise. Almost everyone is in good shape, live healthy lifestyle, look after themselves well, and with better hair quality and length.
To put it bluntly: There are beautiful long-haired women willing to model for the money since they are poor. A Western producer is willing to pay them to model. It's a win-win situation. But there is a drawback. Haggling is part of their culture, so they will haggle their price up. In the West, the prices are often fixed; they will either do it, or they won't, because money is often secondary to reputation.