I had the same name from 2004 9when I joined) to 2008. i was a 'regular' and loved being part of the furniture here.
Then I was spotted by someone who knew me in RL and - although nothing sinister came of it - it could have been absolutely awful. She was a colleague, and it meant that, in theory, she could have searched my posts and learned a LOT more than I would ever want someone I worked with to know about me.
Since then, i name change about once a week. It has its downsides - I feel like I 'know' all the regulars, but they no longer 'know' me - but it can also be fun
Bottom line is, my privacy means more to me than forming relationships on Mumsnet.