around 2008 i was working for a startup incubator.
there were 2 webproperties
a people search engine
a travel social network
a yelp clone
i was in charge of SEO
in it was a major success
the people search engine became part of the biggest websites of the western world, top 10 in europe
the travel social network became a travel guide with more traffic than tripadviser then
the yelp clone became bigger them qype, the then leading yelp clone in europe
all with technical SEO
felt like a superstar
all resources were shifted to SEO and monitization
all 3 webproperties dont exit anymore (sometimes the companies behind them still do)
we did scaleable SEO before we had a product that users wanted.
so by now, I don't touch projects before they are not (near) product market fit. SEO kills if done otherwise.
said that, the people search engine had a 100m exit i think, which was a lot at that time.