I have my Nexus One connected with the USB.
When I visit the File Explorer of the DDMS, if I click on the \"data\" folder the little plus near the name \"data\" disa
I don't think anyone really understands this question. Giorgio can use the DDMS File Explorer to browse the ./data folder on his phone. Pentium10 talks about needing root access on the phone.
Well I a retail Nexus One and a developer Nexus. I have always been able to use DDMS File Explorer to browse the ./data folder on my developer phone but not my retail phone. So I rooting my retail phone would help. I didn't.
So the bottom line is there is something different about the retail and developer phones. Until more research is done you won't be able to browse the data folder on your phone.
Hope this helps.