To go swimming in the social media pool you need to know where the deep end is.

Sinker
The Sinker states they do not understand all the excitement of social media.  They state that it has no effect or benefit to them.  They fight every attempt and turn off every news story about anything to do with any social tool.  They never want to get wet and could care less where the pool is located.  We often think they do not even like being near the water.  Soon everyone around them is using some social network site and the sinker complains about all the invites they get.  Heck, they used to hate email.  This person is easily identified by the answering machine at home that still uses cassettes.  Every so often one of them breaks down and becomes a Treader.  This is usually after getting pushed into the pool.

Treader
The Treader takes the first step in signing up for services to appease the requests of all their friends and family.  They never quite understand all the benefits the tool can offer, nor even how to use have the features.  They were likely pushed into signing up by someone close just to make them shut up.  The treader rarely screams for help and will flounder in the corner holding onto the edge until a cannonball takes them under.  If they manage not to drown and become a Sinker again, they head towards the light and become a Swimmer.  Do not get too close to a treader as their constant whining can sometimes take you down with them.

Swimmer
The Swimmer takes pride in knowing how to navigate numerous social tools.  They coast along seamlessly between sites and often use the integration between them.  They share not only how their day is but useful tips and find value in the tools they use.  Social networks become a knowledge source and place of solace.  This is the high point of the bell curve of users and adoption.  The Swimmer will often cause splashes and kick a treader in the face with no regard.  Swimmers often do not understand why a Treader will not let go of the edge and join them in the deeper waters.  They hate the whiners and ignore them quickly. Increasingly as they see postings of misunderstanding about the social tools they offer some advice and correction making them Lifeguards.

Lifeguard
The Lifeguard is the watcher of the social tool or network they care about most.  They save the newcomers (Treaders) from talking bad about the service by making sure they know how to do specific tasks.  They exceed depth of the Swimmer and are not scared to go into uncharted waters.  This means beta versions of the tool they use.  Swimmers often hesitate before trying a  beta for fear of hurting their computer.  The Lifeguard has made accommodations for testing, like test machines, Virtual Machines or the thought they can always reinstall if something goes bad.  They jump at the chance to get on the most recent version to stay ahead of the bell curve.  Some will become Instructors accidentally by producing a quick how-to video.

Instructor
The Instructor has mastered many social media tools and is looked upon as a knowledge master.  Sometimes they might even be referred to as early adopters for their drive to learn every corner of a new network.  They willingly share information to anyone who will listen and often write long blog postings describing how to use a tool.  Or even worse, screencasts on how to install, configure and best utilize the tool.  The Instructor seems to always be online somewhere, sharing information to anyone that will listen.