Some companies use it as a part of their Social Media strategy which is great if you want to get visual updates, promotions, and more from those companies! I do follow some clothing retailers, fashion brands and magazines, but mostly I like to use Pinterest as my own personal database, or online collage, of things I love.
Are you on Pinterest? Are you addicted?
If not, WARNING, time flies when you're having fun... and it's A LOT of fun!