The Arminian Perspectives blog has a great post teasing out the implications of interpreting passages that seem to warn against apostasy as though they really indicated that the person who "fell away" in reality was never a true believer. Here's a sample, to whet your appetite:
“Do not by your eating destroy your brother for whom Christ died” [thereby proving that Christ really never died for him, and that he was never really your brother]. Rom. 14:15Good stuff. Check it out.