Can you change your online name (gamer tag is the Xbox equivalent) on PSN like you can on Xbox Live?
If so, how do you?
No, this is not possible at present although it is something Sony have talked about and acknowledged as a highly desired feature.
The following is an extract from article on IGN regarding the issue quoting Sony Computer Entertainment America's President and CEO Shawn Layden:
"The road map for feature extension is very long. It goes from here to Hangzhou in China," Layden remarked when I asked about not only changing one's PSN name, but about other oft-requested features like deleting unwanted Trophies. "And all of those things are on there. Yeah, we want to give you more control across your experience and your profile and your presence on the network."
"At the same time, as you'll understand, we don't want to make it so that you can go in, grief a bunch of people in Far Cry, change your avatar, change your username, go into CoD and grief everybody over there. We want to stop that."
When I asked if that issue specifically -- the risk of abuse -- is what's holding up the feature being implemented, Layden answered in the affirmative. Transparency in changing your name seems to be the issue at hand.
Hopefully Sony can work out these issues soon.