I conduct about 80% of my trades via Instagram, and for the past 16 months or so it's been largely successful. Like several others have pointed out, yes, it is unregulated and it does require more vigilance, as there are no mods to handle issues. Occasionally, as with PinPics or Facebook, I've been burned by other traders, though those experiences have been few and far between.
That said, the community is mostly wonderful and it's a mostly positive experience. I like to err on the side of caution, which means being super vocal about asking for photos of the pin front/back, asking if they have references on other pin sites/IG, reminding them to use bubble wrap/mailers (not everyone does this, which I learned the hard way), and always always always getting a photo of the package and a tracking number (and/or paying as goods, if you're purchasing from a seller). Basically, my No. 1 rule is that if you have a bad gut feeling about a trade partner -- or, if they don't have many posts up and aren't tagged in anyone's photos as proof that they've made legit trades -- just say no.
In general, you see the same stuff on IG that you would on, say, Facebook. There are people who, unwittingly or not, trade and sell a lot of counterfeit pins. There are a lot of people who prefer to trade by dollar value. There are a lot of international traders, fantasy pin makers, and new pin traders. There are also a lot of seasoned, well-established traders who are very fair and fun to deal with. If you decide to go the IG route, I'd be happy to PM you the names of some trusted sellers/traders I've come across. Best of luck! 🙂