It's all very well being paranoid on the internet but you have to weigh the risks against the benefits.
If you wish to be identified as a legit seller in this group then it depends on what information has been asked for versus the benefits you gain as being recognised as 'legit'.
If you are being asked for a complete life history and you are only making say £100/year from sales then it is probably not worth it, if you are being asked for your name, address, email and possibly mobile phone number then that would seem a reasonable amount of information to give in almost any case. I have to give that information to buy a ferry ticket !
Remember your name and address is not classified information, and your email address is not exactly a state secret either. You could of course always set up a seperate email account just for trading purposes.