I was just thinking yesterday about what effect all these chemical preservatives have on the microbiology of the human digestive tract. There are various things in tons of sodas and juices to keep any bacteria from growing in them, so what does that do to the ones in your stomach and intestines? I'm sure some have done studies on various ones...
I'm not a biologist though, so I don't really feel like looking them up myself. :P
I think I actually almost completely avoid them myself anyway, just because I don't like most of the worst offenders. I don't drink juice much and tend to get organic and 100% juice, no preservatives.
We definately need more Dr's (PHD's & MD's) looking into this stuff.