What's in a name?

I've tried to make a habit of spending more time in public spaces, and less time retreating into the forest for a change.  I will still have my forest time, but being around others must balance out my times of solitude.

In the previous two visits at my coffee shop, the barista had trouble remembering my first name. She got the first letter right, but I always had to help with the rest. Today, she remembered my name.

It got me thinking...
   - How many interactions does it take a person with an average memory to remember someone's name?
   - Is it easier or more difficult if the stranger has the same name as a current friend?
   - How long do you have to know someone before you give them a nickname?
   - What has to happen to forget someones name?

With all that happens in life... births, deaths, new beginnings, and abrupt endings, in all this musing and making we often get to meet another soul with countless stories to widen our world. What is necessary for people to be memorable?