I am sure you are going to hear many long-winded claims about the veracity of the Britney nipple shot. Mark my vote in the fake picture column. Looks fine at first glance, but under close inspection, there is some obvious Photoshop work being done.
The person who is the source of this picture took a known photo of Britney and altered it, adding a large portion of the left boob to make it look natural. At about 300% (3X) magnification, you can see a large portion above the areola that was obviously blurred using the smudge tool. Magnify a little more, and you can see large portions of the left boob that have been sponged or smudged to try and blend the coloring of the shot together. The big give away here is that this really changed a lot of the shadows of her hair and some locks seemingly stop nowhere. My professional opinion is that this is about 90% a fake picture.
Hmm, J-Unit might have a point, but we're usually "finished" with our "examination" somewhere between 150 and 200% magnification. We'll let you know what we think if we ever work our way up to 3X, but by the time that happens we'll probably have moved on to new study material.