All iPhone 4's are built exactly the same way. it is impossible that millions never had this issue.
When I first got my iPhone 4, I attributed the sudden multiple drop calls to a number of things. It wasn't until I switched back to my 3GS that I realized that it was the handset.
The main issue here is the same as with the 80% screen failures of the eMac, the exploding batteries of the PowerBook 2006 and, well, major problems with pretty much EVERY Apple product since they cut QA and manufacturing cost in the early 2000's : they produce crap. I know this is painful for fanboys to admit, but while the design and ideas are fantastic, the production quality is every bit as shoddy as on a Dell.