Reid Hoffman told the Wall Street Journal every startup should setup camp around a deadly sin:

Social networks do best when they tap into one of the seven deadly sins. Facebook is ego. Zynga is sloth. LinkedIn is greed.

CollegeHumor took this to the next level with seven deadly websites.

The point is palpable: to get deep engagement, make something irresistible as sin.

You got to help people get laid or get paid!

I like to say it's all about love. but get laid works well too. The other one I remember is to help people make money, not save money.

@ifindkarma I still hear @sv_troutgirl 's voice in my head: "paid or laid" RT Startups, pick a deadly sin http://t.co/SAJeUffe (cc @samzeb)

Facebook clearly pivoted. They were aiming for Lust, but people were using it for Pride so they let them.

Lust is over serviced on the internet already and Greed fits lots of traditional business models.

Some of the others have historically been harder to target. People have been trying for gluttony since before there was a home computer business. I'm sure every 5 years boardrooms turn over and a fresh batch of execs said "We can sell computers to women if we build recipe filing software".

This one from 1969 may be the earliest but the same idea crops up again and again.

I think Wrath is the most open target. There have been relatively popular websites on it, but I can't think of a commercial success.

Yelp is wrath. Angry consumers hurl hurtful words at businesses they think wronged them.

Then said businesses have to pay Yelp protection money to save their reputation on the Internet from the wrath of said consumers.

Yelp doesn't sell wrath; it just takes advantage of it.