How many times over the last few weeks have you heard someone raving about Pinterest? It’s the social pin boarding site that’s taking the social media world by storm.

In fact, it’s featured in pretty much every social media prediction post from the past month.

But why is it so popular? After all, it’s not the first sharing/bookmarking/pin boarding site out there. Tumblr, Posterous, Stumbleupon, Wists, ThisNext, IHeartIt and Polyvore all do variations on this theme.

Well, here are five reasons why Pinterest is so popular.

Its simplicity is its advantage

You can’t customise your personal page, it’s not full of ugly flashing graphics and the browsing pages are thumbnails rather than full-sized images.

But this is all to its advantage. It’s clean, clear and incredibly easy to navigate.

Oh, and because they don’t have endless categories, it’s really simple to find lots of content you’ll like in one place. With more and more competition in the social media market, being simple to use is a huge edge.

It appeals to the 20-30 market

Tumblr is becoming increasingly noisy, filled with images of emo teenagers, flashy graphics of Harry Potter and Twilight and song lyrics. Stumbleupon tends to be loved by the techies looking to pass a lunch hour.

For the moment, Pinterest is a breath of fresh air. It appeals to the market which has money to spend and which loves looking at products. .

It’s invitation only – and I suspect that’s keeping out some of the more spammy users. Whether this will change when it’s out of beta remains to be seen.

The Foodies, Fashionistas and Crafters have landed

You know you’re onto something good when the big three have arrived.

The Foodies have been incredibly busy filling up Pinterest with recipes and tasty images, while the Fashionistas are sourcing the hottest new fashion trends. The Crafters share their latest finds, patterns and get a little bit giddy about craft organisation layouts.

It’s fast

Using Pinterest is fast to use, whether on the apps or directly on the website. It’s quick to browse your favourite categories, super-quick to repin something, and easy to share something using the toolbar extensions or bookmarking button. You only have to give a couple of words as a description too.

It’s heaven for businesses

There’s nothing more flattering than seeing your product featured on Pinterest, and if the right person repins it you could see a huge amount of interest.

Additionally, it’s proving to be excellent for bloggers. Pin an image from your blog, whether it’s a product, photograph, plate of food or fashion look, and if it’s popular you could see plenty of repins – and people clicking through to find out more.

For the moment, it’s proving to be one of the most visually interesting ways to spend your lunchtime on the internet. Hopefully the quality will stay high as more and more people join.