I'm not saying it will, but that it's more likely to. No-one knows what technology brings to the table.

Eg. "it is not our intention to sell your photos"

But what if some kickass image analysis startup emerges that can mine valuable data from billions of pics. And then sell that data. So, just like Twitter with its firehose, Instagram licences its data to 3rd parties. They've just ruled that out (except they haven't, because licensing something is legally different to selling it, if not in substance).

It's a lawyer's job to leave terms as much in their client's favour as they can get away with. It would be foolish to close avenues for no reason. There's a balancing act with PR but overall I think Instagram were just unlucky here and handled it well.

Because some day they will want to do the things he is insisting they "have no intention" of doing and this post will come back to bite them.

How will it bite them? The blog post has no legal bearing, and they can just claim they changed their minds - circumstances have changed, etc.