Caradvice is ranked in the top car websites in Australia, just behind sites that are run by big media companies like NewsCorp.
Alborz created a blog on a topic he loves and is passionate about and has turned it into a successful business. I think we see people all of the time creating websites purely for profit, sometimes they work, but mostly they fail. Just check out the sites for sale on sitepoint, most of them are crap. I am just as guilty as anyone though.
I think a lot also can be said for just working on one or two websites at the most and putting everything into them. Running multiple websites in many ways is just not practical and I think you waste time running from one niche to the next. Pick a niche that you love and write good content – it can be as simple as that.
This has worked for me to some extent with my Beijing site. At first I was running around trying to get links, but after a while I realized that if I wrote a funny/interesting/informative post, people would just link to it naturally. I think Google also prefers this. Link exchanges, link swaps and blogrolls are basically dead.
The hardest part to this of course is finding a niche that you are passionate about and is profitable. It is something I am going to have to spend some time thinking about once again when the Olympics are done.