add a "Delete My Account" button or option so People can delete their account themselves.

do this and you will see as more than 10% of your users cancel their account.
i prefer user to contact admin if he wants to cancel account.

If they want to cancel their account, it means they either don't like the site or have no more use/interest for it. Why clog up dbase if they won't use the site? and if they don't like the site, why make them not like it even more by having them jump through hoops and taking their time to cancel the account? they will leave anyway, but if you piss them off , they definitely will tell at least 10+ other people they know why not to use your site. It's basic business/customer relation knowledge and privacy practice. Plus, it will take your time and effort to delete them instead of spending your time improve the site so they actually want to stay?

it s ok, but i give you my personal experience, i had in a social network opcion : cancell account in the menu of contact admin. users canceled account no more than 1% eaxh month.
but in a update, we add option :cancel account in personal menu, and from te first day, many users request cancel theis account.
So i am wondering. why before those users ddidn t do it?

this depends on the image you want to give to your social network, if you have 50000 users, so maybe it s a good idea to display this option in a clead menu. but if you have 10000, and you need more users in browsing etc..., it s better to make option cancell by contacting admin with a feedback, this also will give you idea about reasons and help you to make a better web.
this like a bar, everyone knows where is the door, and he will go out when he wants, but if you put a display in the wall saying : go out if you want. sure that your are giving idea ...
the most important is to have this option.