a good overview on 4 different views on crimea from a washington post blog...
"What follows, therefore, is my attempt not to conclusively answer the question of Putin’s motivation, but rather to lay out a framework for thinking about the different explanations that are out there. I believe this is an important exercise because the different explanations also imply different implications for what is likely to happen in the future, as well as how various international responses are likely to affect subsequent developments"
and some embellishment...
even with four different prospectives, there is a lot of information missing, though... namely the russian experience with post cold war deescalation, russia's factual incapability to place itselft on the same level with the west on legal and economic grounds (and having therefore to rely on "realpolitik"), the nationalist antirussian backlash in romania, moldavia, ucraina and the sensitive situation of russian minorities in these states...
maybe i can find some kind of overview on these issues