Though I am wary of opening up another battle about who is and who isn't vagante, I want to make a general comment about the whole phenomenon.
I have to agree with Serge that when we have to go on elaborate searches to find a line of succession, there's a problem. Or at least the signs of a problem. But the real problem, it seems to me, is somewhat different. The real problem is accountability.
Free-floating episcopates may be Orthodox, or they may be orthodox, or they may be more or less out in left field. What determines this? Well, they do. They don't answer to a hierarchy, after all. Some groups which exist to be more pure than the parent may well be able to maintain their O/orthodoxy over the long haul, especially if they are large enough to maintain some internal mutual accountability. But when things start to go astray, who's going to stop the slide? Well, you can do it baptist-style, where members of the congregation stomp off to other churches. But then, some others may come to take their places.
The accountability issue functions on larger levels too. The Episcopal Church clearly has a serious accountability problem in the House of Bishops. The mechanisms are there, but seriously out of line bishops are not called on the carpet. From a Protestant perspective, Orthodoxy and Catholicism both have accountability problems because they refuse external criticism.