I started https://www.pubexchange.com in 2013 and have been running it solo ever since. PubExchange is a platform that helps publishers establish traffic exchanges with other sites (similar to a social network) so that they can promote one another via widgets, social, and in-article links. It's been profitable since 2014 and I work with over 600 sites, including HuffPo, Refinery29, and POPSUGAR.
The tech wouldn't be the edge here. Contacts with these high flyer publishers would make or break the business.
I actually don't value contacts very highly, and almost never ask for intros or leverage previous relationships. For a one-person company, intros are a time-suck, since the recipient of the intro will tend to take calls or meetings even if they are not interested in the product, just out of courtesy. Instead, I attribute a lot of my growth to building a product that addressed a clear need, and then using Linkedin to pitch the right people. Now that a fair amount of sites use PubExchange, most sites that join come through referrals, but most of those are from people I did not personally know before launching the platform.