@Alice.in.Wonderland -
Here's how the ownership works: once something is posted, that post becomes the property of MyPTSD.
If a member wanted to use their posts or information therein for a memoir say - yes, MyPTSD would need to be asked for permission to do so. And that has happened in the past, and permission is granted.
If a member - or guest - wanted to use a fellow members' content, MyPTSD would not grant that permission. This is actually how we protect your content, here.
If you came across your own diary posted in someone else's blog, say - you'd tell us and we'd deal with getting it taken down.
For images: it's actually helpful to imagine that the image is an actual physical thing.
So, you take a picture with your camera. You can print unlimited copies of it. You can pin one to your media galley here, another to Facebook, another to your wall at home, you could give them out as gifts...
If you buy a single print of an image at a store, you have one print, and you can 'hang' it one place. If you took that print to a copy shop and made five copies and posted them also in your office at work, your bathroom, your cousins house...you have essentially stolen those copies; if you wanted five of them in the first place, you needed to have paid for five.
If you found a picture on the street and didn't know where it came from - you'd assume it belonged to someone, probably. That's the way to treat images found on the web.
Copyright and DMCA exist in order to protect the owner of the picture you might find on the street, only the 'street' in this case is the Internet.
If a owner has made reproductions of a picture available for 'sale' - such as through an image supply house - and you purchase one copy, you can use that one copy wherever they say you can. If you post it here you are essentially hanging it on a wall in a big building called "MyPTSD", and we are now responsible for it.
If and when you want it back, you ask us, and we decide whether or not we can give it back.
Back to text: you post text here, we now 'own' it, and we protect you from a random individual finding it, making a copy, and putting it somewhere else.
This is an oversimplification, but it's the foundation of all copyright law. The 'fair use' concept exists because certain kinds of applications (scholarly ones being the most common) depend on sharing knowledge and materials; and so, educational institutions in particular are granted the right to excerpt from other works without paying for it for the purposes of educating others.
I hope this has helped.