Yes, it can be flush mounted either by hanging on screws with the built-in attachment points or by ordering a separate hanger plate. I opted to just set it on the screws directly since it's light enough to not need any reinforcement... The power cord is on the side. You will need to take it off the wall to add or remove pix from the USB though.
The back of the unit is not flat; it is the shape you would get by placing a small paperback book on top of a larger book. The part corresponding to the small book is flush against the wall, but there is a gap between the wall and the rest of the frame. The cord sits in this gap. Hope that makes sense - it is hard to describe without a picture.
All the previous 3 answers are correct. It can be wall mounted easily. There will be no problem with the Electrical Cord. This Photo Frame gets 5 stars in my opinion. High Resolution w/back-lite makes it a winner. I have mine loaded with about 3,000 High Resolution Photos and it sits on a unused counter space in our Kitchen.