From some quick interneting,

Drinks with HFCS contain ten times the carbonyls than drinks sweetened with cane sugar. From what I understand, those are bad, diabetes-linked thingies.

So far, this is the only solid bit of evidence showing HFCS to be the direct culprit. Everything else I've found is linked to increased sugar consumption in general, which means HFCS is an indirect culprit. (i.e., we get more sugar becasue HFCS has become so ubiquitous, but if we ingested as much cane sugar as we do HFCS, there would be similar bad things happening.

Also worth noting is that the variety of HFCS in soft drinks has about 10% more fructose than cane sugar (i.e., sucrose. One sucrose molecule is one fructose molecule bonded to one glucose molecule).

This is a tricky area to try to research. Most academic findings show health risks of HFCS, but not in comparison to similar consumption of pure sucrose. The studies showing no adverse affects over sucrose are all industry-funded studies.

I found this info at the wikipedia entry for HFCS and at two blogs:
thefitshack.com and livesugar-free.blogspot.com

oh, and some other tidbits gleaned from those blogs:

the crystalline fructose is at least nominally different from HFCS, but they're both sweeteners derived from corn starch. start with corn starch, do some enzymatic reaction to turn the starch into glucose, then do some more enzymatic stuff to convert some of the glucose into fructose.

I had heard some of the problem with HFCS is that frustose is processed by your body differently, more like a fat than a sugar. What I found is that fructose is only metabolized by your liver, rather than throughout the body, as sucrose is. Too much fructose and your liver gets fatty deposits.

But since sucrose is just fructose and glucose bonded together, does sucrose break down into glucose, which than has to go through your liver? I dunno. If so, then we're back to the HFCS has 10% more fructose than cane sugar problem. Or maybe your body metabolizes sucrose such that its fructose doesn't get to your liver. Again, I dunno.

Then, there's the fact that, in my experience, things sweetened with cane sugar simply taste better. When I was In Venezuela, I had occasion to try both Pepsi and Frosted Flakes made with 100% cane sugar. yum yum.

Well, I think also the quasi-addiction to supersweetness that is a byproduct of consuming HFCS probably adds to the problem. So again, HFCS as an indirect culprit, but if you get kids on the stuff young enough, they're consuming so much more sugar and calories than they would otherwise, raising their risk of diabetes, etc. etc. And as I said in my original post, I don't see any harm in NOT eating it. We know the body works more efficiently on REAL/whole foods. All things in moderation.