When you reload the family later you might find that it doesn't update properly or that if you get around to creating more types you'll have this rogue original one to replace.
Simple solution, create a new type right away and you can call it default for now. Rename it later if you decide you don't like it or need it anymore.
With the 2011 release we can test parameters in-canvas. In the past any attempt to drag a reference plane or element that was constrained by a parameter/dimension would generate an error message. They provided this in an effort to make the Family Editor more relaxed about this. When you select a reference plane that has a dimension and parameter associated with it and drag it to change the size of a family Revit will just let you do it.
The change(s) you make is/are applied to the current type.
It becomes more important to consider a default family type in light of this. You probably don't really want to mess up specific type dimension values. If you are careful to make the default type current and then adjust the family you'll avoid creating a problem. Then again you can just reset all the values that get adjusted. Either way just be aware that you can manipulate them in-canvas and you can mess up existing family type parameters.
If you'd like to watch a video that discusses this new direct manipulation of families then check out Autodesk's You Tube Channel, THIS ONE narrated by Chico Membreno. I've embedded it here too.