Hi, you are very welcome to do any research on the OSM community :)
Please also check out this page, to know about previous works and how we understand a coop with the scientific community: http://wiki.openstreetmap.org/wiki/Research
Every user has a unique ID that is [tracked in edits][1] ("changesets"). So you can use the [API][2] to start with your analysis. But to do more/global processing, I highly recommend to make use of our [history planet][3], so you have a definite dump and can work locally. But currently there is kind of official user ranking out there. There are some unoffical stats, as ['how do you contribute'][4] for example.
But you need to pay attention on just using that simple metrices on the work of users/the community, as there might be local aspects that you need to keep in mind (e.g. imports or availability of aerial imagery has an influence on the workflow etc...)
Please also note, that there are various other [communication channels][5] that are used differently on the local OSM communities.
P.S. Just one more hint: Please be aware that a lot of people are very concernd about their privacy etc. So AFAIK even the OSMF won't allow you to get more detailed informations e.g. "statistics about signup email account TLDs".
[1]: http://wiki.openstreetmap.org/wiki/Elements
[2]: http://wiki.openstreetmap.org/wiki/API
[3]: http://wiki.openstreetmap.org/wiki/Planet.osm/full
[4]: http://hdyc.neis-one.org/?!i!
[5]: http://wiki.openstreetmap.org/wiki/Contact
