[aclements18]

It still costs money to acquire new users. It's easy to think when something becomes a household name there is no need to keep spending to bring new users on. As with most social sites the bigger the network is the harder it is for competitors to come in and steal their position. Pinterest user base is still "only" around 50 million. Thats 5% the size of Facebook.

Additionally the markets are not treating tech stocks so well right now, this might last another three months, and it might last a year and a half. What you know for sure is that you don't want to go out and try to raise money when the market is really down. You'll be terribly diluted if you're even able to raise money at all. They get what you can now, because they don't know how long it will be until the IPO.

These are only a couple of the considerations, if they are planning an IPO very soon then there's a completely different motivation. Hope this helps.