I was fortunate to hear a talk by one of the partners at Andreessen Horowitz, and he made this point: You want your idea to have three attributes:

1. Growth – it needs to be a naturally-resonant or ad-resonant property
2. Stickiness – once exposed, people need to come back of their own volition (daily or weekly)
3. Monetization – you need to be able to make money from the visitors

Viagra is a great example:

1. Viagra is super resonant
2. Customers come back every time they want to have sex, and…
3. It’s $10 a pill. It is a great product.

Google also has all three:

1. Google grew very quickly (very high resonance)
2. People come back to Google every day, and…
3. Google found ways to monetize the traffic.

Facebook is another example:

1. Facebook grew very quickly (very high resonance),
2. People come back to Facebook every day (he said that 65% of Facebook visitors return every day! Sometimes 10 times a day), and…
3. Facebook found ways to monetize the traffic with ads.

Twitter is an example of something less perfect:

1. Twitter grew very quickly (very high resonance)
2. Some people come back to Twitter every day (but a much lower percentage than FB, like 15%), and…
3. Twitter has had trouble finding good ways to monetize the traffic.

Bottom line: If your idea can combine growth (resonance) and stickiness and monetization, you are golden.