First of all though, I'll give you some history of what I've personally seen. ShareMy.Name seems to have gone through several different phases from where they simply acted as a username/password and personal details depository so that other sites didn't and so you would have to provide the same username and password to all sites, and a malicious (or hacked) site could get all your details, to where you needed to enter a regenerating accesskey (sort of like those two-factor ID things) to the current state where you get an accesskey assigned to you when you sign up, and send that key (supposedly) to ShareMy.Namen where if the accesskey matches an account, it asks you if you want to send the data the site has asked for back.
You can see a demo here: http://sharemy.name/test_sendback/
if(document.forms['sharemyname']) r(); else alert('We tried everything, your going to have to enter aNwluiUMqk manually; or, they do not support ShareMy.Name.');
Which tries to send the request to Share.MyName so that you can verify whether or not you want to send certain details to the site.
For the moment lets ignore the fact that you could just ask the user to input their accesskey in a form, and they would readily do it, or the fact that every site gets sent the accesskey, and assume that the bookmarklet is the only way to get the data, and the accesskey is not sent back.
They give us the accesskey (when they set the cookie) no matter if the user agrees to give it to us on the sharemy.name page.
But ignoring the fact that we are given the accesskey initially (this is an easy fix with no real ramifications - what is harder to fix is people overloading and subverting the page in such a way that the bookmarklet fails in its job), and the fact that users are encouraged to enter their accesskeys into unknown forms ('We tried everything, your going to have to enter aNwluiUMqk manually; or, they do not support ShareMy.Name.'), there is still the problem that the site is sent the accesskey by default.
This is a problem, because when the user say gives the their First Name, Interests, and Accesskey, they are essentially giving the site all of their information, because there is no additional identification required to get information about the person other than the accesskey.
And even more than that, since the key is permanent (from what I've seen) they have access to your data indefinately.
Now I realise that this could all be fixed simply by requiring the user to be logged into their account when agreeing to share details, but I think without an expose on the ramifications of their current design, nothing will change. And its fun to write about the havoc one can wreak.