I've had my Note 2 since back in April, it has been amazing, but as of this past October or so, I get a HORRIBLE echo of myself when talking to others. It doesn't seem to happen with EVERYONE I talk to all the time, but seems to ALWAYS happen when I talk with my husband. He recently upgraded to a Note 2 from a Razr Maxx. I am not sure if the issue is between the two phones, or if it is entirely on my end. Someone has already suggested that I disable voice privacy on calls, but that has made no difference in the echo.
I have this same issue from time to time-- even on calls.
In fairness to Samsung however, it occurred occasionally on my HTC Trophy too. Honestly, I think it's a Verizon issue, and not specifically a Samsung, or Note2 issue.
It could be a technology issue-- some flaw in the system which results in random bits of code floating in cyberspace, resulting in the feedback! ;-\