Thoughts on putting controls in the top horizontal bar?

Question

Is there any authoritative overview of the pros/cons of using the topmost menubar to host action items that change depending on context? An example that comes to mind immediately is Microsoft's Skydrive - if you select some items, the options change accordingly:

This seems great for basic CRUD actions on things like lists of documents or items where the available actions change depending on whether or not you're selecting one item (View/Rename) or multiple items. I just don't see it very often so I wonder what the drawbacks are.

Answer 1

Google Drive uses a similar pattern. The drawback is that users might start to ignore the bar completely or not even think to look there. I've noticed that users first look for action button close to the item to be acted upon. It took a several times before I could explain to some users that they had to look in that top bar if they needed to do X,Y, or Z.