Oops, aerial trouble with the new iPhones and southpaws.

http://news.bbc.co.uk/1/hi/technology/8759590.stm

I'm a leftie when it comes to the iPhone and I haven't yet been able to reproduce this problem ... I've even tried going to youTube and duplicating the hand positions and still can't get the bars to drop.

Might be a per-unit issue, or perhaps depends on your service area?

i can replicate this issue on my wife's iPhone 4. if i place the phone in a iPhone 3G rubberized case and hold it the same way then the problem no longer exists. but without the case i can hold it and make all 4 - 5 bars disappear and connectivity is completely gone (takes about 12 - 15 seconds of holding).

Does the reception drop when you hold/touch the antenna band? A design flaw?
Users are reporting diminished or lost reception when they touch the stainless steel band around the iPhone 4's middle. This band doubles as the main structural element and the phone's antenna.
As evidenced in multiple videos posted to YouTube, when the iPhone 4 is gripped in such a way that skin touches this band, the signal strength bars appearing in the upper left corner of the screen drop within seconds.
More info

(Sorry 'bout the double post. I did not see that someone else posted on this subject! Too late to delete it.)

One of the guys at work got one yesterday, we couldn't reproduce the problem either. I even wetted my hand before holding the phone.

I think it's a production flaw more than anything, not unlike the yellow screens.

They say it tends to be much more pronounced on the edge of cell range. If you are in an area with a good signal you probably can't reproduce it.

Try putting a key or something metal across it.

Consumer Reports says this is common among all cell phones and not just with the iPhone:

'Consumer Reports': iPhone 4 signal issues aren't unique