Most of the iphone 4 users have problems with the antenna system .
When you touch the down left corner of the phone the signal bars go down untill you will have only 1 bar.
This problem can also drop calls.Steve Jobs say that it isnt a big problem(!),we can fix it using a bumper from apple but you have to pay 29$!
So we think that the apple have to offer free bumpers/cases for every single iphone user or to recall the iPhone4.