That may be true, but there are many many stories of people reporting difficulties with diet sodas. Who is conducting 20 year double blind tests on each of these diet soda types? How long has this stuff been out? I don't even know of any 5 year double blind scientific studies in progress, do you?

Surely you don't always believe marketing hype that XYZ is just terrific for you all.

See the problem is the converse is also true, there is not a shread of scientific evidence that drinking diet sodas for 5 years will NOT hurt you. Since scientific evidence is both lacking and no one is conducting scientific studies, and too many are reporting hearsay accounts of difficulties with diet soda, why increase your risk of problems down the road?