I'm not an Instagram user, but wow, are you kidding me?
Good for Instagram. They offer an amazing service for free. If they want to use yours pics, they should be allowed to. At least they warned you in advance.
"but the photos I take are MY property and mine alone." - FAIL. Whenever you upload something onto the internet, you might as well say goodbye. Who knows how many people have copied your photos, and who knows what have been done with them. If you want to keep them private, don't put them on the internet. Are you new to the interwebz or something? You should know better.
Why the hell should they compensate you? You're using their service for free, now it's time for them to receive something from you.
I hope you don't have a Facebook account, and if you do, why haven't you deleted it yet? I'm sure they've done more than you can imagine with your information.
*if I get a warning point for this, that is complete BS. This is a forum, and I'm just voicing my opinion*
I couldn't agree more! being a professional photographer I make sure the images I post online are properly watermarked and at a low enough res they wouldn't be usable. stuff i post to instagram is for fun only.... i would NEVER post anything business related that I wouldn't want stolen on that account