Let me be clear about one thing up front: as I write this, you cannot buy an advert on Instagram. There is no self-serve tool, no announcement, nothing official. What there is, though, is Facebook owning the platform since last autumn, a user base that keeps climbing, and a business that eventually has to make money. I would be very surprised if paid placements are not on the way, and I think brands would be daft to wait for the press release before they start thinking about it.
So this is a piece of informed guesswork, not news. Treat it as such.
Here is my reasoning. Facebook did not spend that kind of money on a photo-sharing app for fun. Every acquisition of that size eventually gets pointed at revenue, and the obvious lever is advertising. Facebook already has the ad infrastructure, the targeting data and the sales relationships. Bolting Instagram inventory onto that machine is not a huge technical leap. The question in my mind is not whether it happens but what form it takes, and how heavy-handed it feels when it does.
The risk for Instagram is obvious. The whole appeal of the feed is that it does not feel like a shopping catalogue. Push adverts in clumsily and you dent the very thing that made the platform worth buying. My guess is they will move slowly and make the early formats look native, closer to a nice photo from a brand you already follow than a banner.
If you run a brand that suits the medium, the work worth doing now costs nothing and pays off either way.
Build a real audience organically while it is still free. Post things people actually want to see rather than product shots with a price on them. Work out whether your brand even has anything visual to say, because plenty do not, and forcing it will show. Watch what the early brands on the platform are doing well, and copy the instinct rather than the exact post.
The mistake I want to warn against is treating Instagram as a straight extension of your Facebook page, scheduling the same content across both. The platforms reward different behaviour. A link with a bit of copy is fine on Facebook and falls flat on Instagram, where anything that looks like it was made for somewhere else tends to get ignored.
None of this is urgent. There may be nothing to buy for months, or the format when it lands may not suit you at all. But an audience built now is an asset you keep whatever the ad product turns out to be, and that seems like a sensible bet to place while the entry price is zero.
