Morgan Spurlock actually did try this. It is an extra on the DVD for Super Size Me.
Homemade fries from a diner started to rot in less then a week. McDonald fries didn't. I'm sure this probably goes for all processed fries (From Wendy's to frozen) but real homemade steak fries will indeed mold.
McDonald's fries are actually made with top quality potatoes and don't have any preservatives or chemicals in them. What you see is what you get, in that sense.
Kara's right about how fries petrify before they rot. Working in restaurants has taught me a lot about the reality of food and has cleared up a lot of misconceptions about fast food restaurants and what their food really is. I can't defend the meat that's used in fast food restaurants (as nearly all of it, from every restaurant, is mixed with chemical flavorings and preservatives in order to enhance flavor and extend it's shelf life) but I can certainly defend the fries.
The potatoes that McDonald's uses are fresh cut and then IQF (Individually Quick Frozen), which is a process of flash freezing something. No chemicals, no preservatives, nothing. The potatoes are then shipped on refrigerated trucks to McDonald's locations all over the country. Once they arrive at the McDonald's of their destination, they are kept frozen until they are needed to be used. As they are needed, the fries are pulled from the freezer and cooked in untreated oil.
*Untreated = 100% pure oil, with no additives.
Like I said, I can't defend the meat, but I can defend the potatoes.
But, with that being said...I've seen meat that has been sitting around for quite a while and, using my professional experience, I can honestly say that what you see in that picture isn't far from the truth. And, I'll tell you why...
If you leave RAW meat sitting on a counter somewhere for a year, it will get so rotten that it will literally liquify and disappear into a puddle of filth. As the air gets to the RAW meat and bacteria invades the proteins contained with the meat, it will eventually get eaten alive and broken down to such a degree that all parts of the meat turn into liquid.
Now, if you leave COOKED meat sitting on a counter somewhere for a year, that
won't happen. The reason that won't happen is because when you cook meat, you are changing it's chemical makeup. You are literally changing it's scientific composition.
For instance, putting heat to protein will "cook" it, which is nothing more than a drastic change in it's chemical makeup. The protein tightens and seizes upon itself, which firms up the meat as you cook it. Protein fibers in meat, when raw, will stay "loose", which makes raw meat have a floppy consistency. Protein fibers in meat, when cooked, will tighten up, which makes cooked meat have a firmer consistency. Anyway, as these changes occur, so do the potential reactions from bacteria and air. This is exactly why the cooked meat in that picture doesn't look like what you would expect it to.
FYI - The potatoes used for the fries also go through changes as they are cooked, which is why they don't look like what you would expect them to.