According to a recent French study, consuming just 12-ounces of diet soda per week increases your risk of developing Type 2 diabetes by 33%.

You can read the whole article if you want, but I'll paste the first paragraph here:
Yet another study confirms what people have been saying for ages: Stop drinking diet soda. Like, right now. Drinking just one 12-ounce can of an artificially sweetened fizzy drink per week can increase your risk of Type 2 diabetes by 33 percent, French researchers found, and given that most people don't stop at a single weekly serving, your real risk for diabetes could actually be much higher.
I swore off diet sodas over 10 years ago because I started reading some pretty disturbing stats about aspartame-poisoning and I learned that Splenda was developed accidentally while researchers were trying to develop a new form of anti-freeze for cars. So, I decided that I would only drink regular sodas from that point on. This way if I do give myself Type 2 diabetes, it'll be from good old fashioned sugar (or high-fructose corn syrup, whatever).

Seriously, though, I've been making an effort to eliminate even high-fructose corn syrup from my diet. It's amazing how many products have it as an ingredient these days. And we wonder why our country's obesity rates are so high.