This seems like a natural move for Pinterest, and due to the nature of its content I think the ads have the potential to be highly relevant to the user. Maybe long-tail products could get an even better channel to reach interested customers?

How about reversing it? Help users search through various products, using what you know they like as a guide. Find deals for them. Instead of collecting data on users and using it for advertisers, make vendors give you tons of data and use it for your users.

That is a very interesting idea. I am wondering if monetized recommendations can be done algorithmically, which might be the case with their interest graph. However, if not and they are targeting long-tail ads it might be better to follow googles lead and do something similar to adwords. Do you have an intuition on this?

If you're chasing long-tail, it might be better to do something like Pandora. Let people fill in aspects they like (or figure it out from their pins), then find products that fit the criteria. "We see you like sky-blue and polka dots. Here's a purse from a designer you've never heard of, all the people who like it, all the pinboards it appears on, and an exclusive 5% discount if you buy through this affiliate link."

What's your idea on monetizing these websites?

I'm sure there is some good idea, just like becoming a prostitute is not the only way of making a living.

Perhaps it does not make much sense to make such websites if "advertising" is the only viable option?

Unless you can convince people to pay for your service, you can either openly use them as advertising platforms or you can be sneaky and sell your data to advertisers behind the scenes.

> sell your data to advertisers behind the scenes.

Doing this is way too risky. It puts your company at risk to secretly sell this data. Imagine if word slipped about this. It could easily landslide into losing half your user-base and eventually the rest of them.

Haha, read my mind! Even if you sell behind the scenes, a profit focused company can't really say no to advertising.

Pintrest is mostly made up of (1) images/photos and (2) real world merchandise of some kind. They could create a platform for selling printed copies of images/photos on pintrest and they could take a cut of the revenues, and maybe even go into easy distribution and scale of physical products shown on pintrest with a cut of revenues as well. Probably other services they could combine with the content as well in other ways with some creativity.

How big is the market for printed photos? How is taking a revenue cut from products really that different from advertising? It is non transparent affiliate marketing which is worse than transparent advertising.

I cannot imply that advertising should be removed, unless the customer financially pays for the service - any company (especially public) will use advertising in some form, or else it is just lost revenue.

I guess the only other option would be to build paid services, like app.net, but that is a completely different revenue model.