MSG is a "flavor enhancer," with one slight problem -- some people are allergic to it. Most people don't seem to care much either way, but a small number of people seems to have bad reactions to it. If you ask people in the industry who sell it, they'll tell you it's quite safe, but there are others who claim that it's potentially lethal to some (very, very few) people.
The first time I found a menu where every link was just a link back to "currentpage#," I didn't know what to make of it. Strangely, I've seen this exact same code multiple times; this suggests that it's not just an isolated burst of insanity, but a "technique" someone has recommended -- or perhaps some exceptionally psychotic software vendor wrote the code and is sharing it.
Since I first wrote this, I've seen a news story about e-commerce sites getting abused by users who alter forms to set new (low) prices on goods they wish to purchase. If the sites had done their own internal validation of data, rather than relying on the user's browser, this might never have happened.