Honestly, I can't recall any ONE single turning point that was like what you had laid out in your initial reply. There has been any number of them that I find equally or greater than the last.... pay sites, clips stores, hosting, email, mainstream...
While I have always made good money in adult, when 2007/2008 hit, it effected me the same as everyone else. However, as a fetish or niche provider, much less so. I decided to diversify. I went into the hosting side of things, and after some tinkering I found some niche markets that were insanely profitable. From there we screwed around in some mainstream and other markets over the past 5 years, and found some mainstream marketing stuff that was even more profitable than the stuff before.
I would love to say I am a genius, but I simply follow the money, it's really always been that simple for me. As long as it's legal, the web is still the wild west and there is sooooooo much money to be made. Especially if you know some level of marketing 101 and think outside of the box. The biggest issue for me was holding on too long to the 'glory days' when I should kept innovating and listening to the trends as the ground of the industry was shifting.
I love adult, and do not expect to ever leave it (especially my core niches) despite the ROI and business model has changed dramatically. But at the same time, diversity is never a bad thing if you can effectively manage it. I have invested in a lot of automation to help do that, not only in regards to minimizing labor expense in the number of bodies, but to dumb shit down to the point I can grab anyone off CL and have them doing the work within a few hours. That is a massive cost savings I can tell you. Plus they tend to work out much better than hiring people in the industry who tend to be lazy and apathetic. You need people who are hungry for an opportunity.
That being said, each venture has made me more than the last so it feels a lot like a game of leap frog. It does get a lot easier as you apply what you've learned to the next project and things go much smoother. People who know how to making money online really should be able to keep doing it fairly easily. If that's not the case, you're fishing in the wrong hole.
