I think the reason this is affecting some people and not others is not a case of location, but a case of the person using it. I get signal loss on my UK iPhone 4 so I went back to the store and they had no idea what I was on about, they said their demo phone was fine. I try their demo phone, signal gone within 30 seconds. The store manager then went on to try my one I'd been experiencing the issue with, nothing happened.
I think this is caused dependant on how conductive you happen to be, does anyone scientific have any idea if humans can be more or less conductive than one another?
My thoughts exactly. I highly doubt that the issue is related to location, inconsistencies in the hardware, or even variations in static electricity from person to person like some have suggested. I think Kuro is exactly right (sorry if this has already been discussed somewhere else). I'm a biomedical/electrical engineer and I deal with this type of electrical interface all the time. There are HUGE variations in skin conductivity from person to person. For example, if a person has dry, calloused skin, their skin is likely to be a far worse conductor than someone with soft, moist skin and should cause less of a problem. There are many, many variables that would have an effect on the conductivity, so it's not at all surprising that the problem seems intermittent.
In addition, the human body is an excellent conductor of any kind of electrical noise. I'm no antenna expert, but to have such a direct electrical connection between the phone antenna and such a noisy source seems silly.
I'm curious to see if the problem caused by bridging the two antennae is lessened by turning off all other radios (wifi, bluetooth, GPS). I would think that would at least help to eliminate some interference.
It seems like more of a hardware problem to me, but it will be interesting to see if Apple can work some magic and come up with a quick software fix. I hope they do, because I'm holding off on getting mine until this is resolved...