Especially for all Blackberry and iPhone users - The manual says it all!
Blackberry Bold 9700 Safety and Product information guide. Page 18. It says "keep the BlackBerry device at least 0.98 in. (25 mm) from your body when the BlackBerry device is transmitting."
Complete manual can be viewed at - http://docs.blackberry.com/en/smartphone_users/deliverables/11261/BlackBerry_Bold_9700_Smartphone-US.pdf
iPhone 4 Product Guide - "keep iPhone at least 15 mm (5/8 inch) away from the body.." Page 6.
Manual available at - http://manuals.info.apple.com/en_US/iPhone_4_Important_Product_Information_Guide.pdf
We hope since the handset manufactures are well aware of this problem themselves , in future they pay more attention in this aspect, invest in better technology and come up with a better product.