Almost everyone have heard about Plentyoffish dating site. There was a big buzz about it (and its adsense money) on the different sites several time ago, so my first post and little investigation will be dedicated to Plentyoffish and its owner Markus Frind.
Markus Frind, Number 1 individual Adsense earner in Canada. He makes more than $10,000 per day! This is what Markus say about himself: "I’m also the largest individual adsense publisher, the only site in the top 100 run by one person etc. Plentyoffish is the 3rd largest dating site in north america after yahoo and match." 
- At Aug. 27, 2003, Markus Frind (markus007) has made posting on WebmasterWorld forum  : "I make about $40/day off 1200 visitors. No idea if that is good or bad."
- At Feb. 27, 2006 he has published a photo of cheque for 901,733 CAD  (Nine hundred one thousand seven hundred thirty-three Canadian dollar, about $800,000 USD!)
Good growth, isn't it?
$800,000+ USD Adsense check
Just some raw information about plentyoffish.com:
- Pageviews/mo: 500 million 
- Platform: Windows Server 2003, Microsoft-IIS/6.0 , Microsoft ASP.NET 
- Servers : 2 main servers (database server and web server)  and several additional servers 
- Google Pagerank: 5
- Alexa Rank: 679
- Site expenses: $5,400 for hosting/month, Instant Messenger is around $8,000/month. AdWords expenses are not disclosed.
Some interesting information about Markus Frind
Marcus Frind is a good IT & math specialist. Let's examine a excerpt from his comment :
"What I keep saying is that Plentyoffish runs on a handful of servers everyone else needs hundreds of servers, not just one big dating sites but all the major dating sites. Many other dating sites have tried to stay free and they have all crashed and burned because the costs where so huge. Webdate.com being the latest one.
A few years ago I created a algorithm that found sequences of primes several thousand times faster then the other fastest known algorithm. [link] People used hundreds of computers and super computers to find the last record over the course of 5 years. I found it on a single machine after a few days.
Plentyoffish is built the same way, it requires a fraction of the infrastructure everyone else has, and its built on technology that can't be cloned and is 20-80 times faster then what every other dating site and social network has."
Some Key features of Plentyoffish success:
- Interesting and easy-to-remember domain name.
- Site Simplicity. Easy navigation and plainness. No AJAX, no WEB 2.0, just naked functionality. Ugly design, but there are interesting opinions about that, see 
- Membership is completely free.
Other Sites of Markus FrindMarkus Frind has a bunch of other sites, running adsense, but they are not so successful as Plentyoffish. Some of quite interesting Markus Frind's sites:
- poemsandlove.com : Love Poems And Quotes - Romantic Love Poetry & More
- arthistoryguide.com : Art History, Artist Biographies, Art Posters, Art Periods
- fantasies101.com : Sex Fantasies, Sexual fantasy story, free sexual fantasy, sex education LOL!
- fundatingsites.com : Online Dating Service Guide
- traveltocanadanow.com : Travel to Canada: Tourism, Accomodations, Travel Planning Guide, and Tourist Attractions
- traveltousanow.com : Your Travel and Tourism Guide to the United States!
At the end
At the end, interesting part from Markus Frind interview  about future of Internet advertising:"Adsense and YPN will be standard components of any business models. There will eventually be a massive market place where you just select a age range, city gender etc and your ads will be shown to people matching your demographics. More tools will be developed to track users intentions and monetize them. If you own a site about horses and someone was thinking about buying a car a week ago while searching the net, your horse site may display car ads. We will eventually see online ads approach the ROI of offline ads or even exceed them as monetization of intentions\preferences takes hold."
- The Paradigm Shift » Blog Archive » Small Companies & Google Adsense is the future
- Techcrunch » Blog Archive » The Power of Digg
- The Paradigm Shift » Blog Archive » Microsoft Asp.net 2.0 Performance.
- Plenty Of Cash for one-man band PlentyOfFish.com
- Giant POF Adsense Check. Online Dating Insider: Online Dating Industry News
- Markus "BigFish" profile
- Online Personals Watch: Online Personals Watch Interview-CEO of Plentyoffish.com, Markus Frind
- Titan Biographies: Markus Frind
- Interview with Markus Frind - AdSense Millionaire (Reviewed at WorkHappy.net)
- The role of anti-marketing design
- 30.000 unique visitors /month = 20 usd / month?
- Exclusive Interview with PlentyOfFish.com creator and owner, Markus Frind - Web Publishing Blog
- Netcraft What's That Site Running Results