The tags are initially viewable only to a subset of iOS viewers in the US. Most of the early ad partners are fashion brands like Kate Spade and Warby Parker. Expansion to Android, video ads and other countries will follow as Instagram figures out how it can display and recommend products. Eventually, you'll have the option of saving products you like so that you can buy them later.

Despite what you might think, Instagram isn't taking a cut every time you tap a "shop now" link. Instead, it's all about convincing advertisers to line up -- they may be more likely to pay if they know that they can turn your ad view into a purchase within seconds. Also, the upcoming save feature is a not-so-subtle way of taking on Pinterest. While Pinterest isn't limited to saving products from ads, you might have less reason to check it out if you can bookmark inspiring products on Instagram.