When does constitutional dicta become law?

In its 2005 decision in Lingle v. Chevron, the Supreme Court authoritatively  discussed and appeared to resolve an issue that was neither essential nor particularly relevant to the issue on which it granted cert.  (As briefly and simply as possible, the issue in Lingle was the relationship between substantive due process and regulatory takings; the issue I'm interested in that the Court appeared to resolve is the precise reach of the heightened scrutiny for regulatory bargains developed by the Court in Nollan v. California Coastal Commission (1987) and Dolan v. City of Tigard (1994). The relevant parts of the decision appear in Part III of Justice O'Connor's Lingle majority and are not discussed in Justice Kennedy's brief concurrence.) 

The Court had expressed a similar conclusion, also in dicta, in a few recent decisions, but it had never come out as boldly and prominently with its conclusion.  What was especially surprising was the fact that the Lingle decision was 9-0, and that at least three justices (including Justice O'Connor, who wrote Lingle) had previously dissented from various prior cert. denials that had concerned petitions raising this very issue. In those dissents, the justices explicitly stated a proposition counter to the one they signed on to, as dicta, in Lingle.  Furthermore, ten years earlier the Court had vacated a judgment of the California Court of Appeal that was consistent with the Lingle dicta and remanded the case back to the state court, thereby setting in motion a chain of decisions in lower federal and state courts that is inconsistent with what the Court has now declared, by dicta, to be the law of the land.  Now obviously, the Court and individual justices are free to change their minds.  But in dicta?  Without a case before the Court that squarely raises the issue?

So my request, dear prawfsblawg readers and especially commenters, is for other, similar instances of this phenomenon of dicta, repeated over time and in an increasingly authoritative manner, potentially hardening into law -- a phenomenon that appears to me, in my relative jurisprudential ignorance, to be fairly odd.  What have the implications been?  For example, may those state courts that had earlier followed what they thought was the Court's preferred direction now change course, if they are so inclined? Are they required to do so, as a matter of federal constitutional law?  (Obviously, they can reaffirm their earlier decisions as a matter of state constitutional law -- and states typically have analogous takings clauses in their constitutions, that they often, though not always, see as coextensive with the federal constitution.)  On the other side, to what extent may litigants continue to make the argument that the Supreme Court's statements are merely dicta, now that  the dicta has been repeated multiple times and in a manner that is explicitly authoritative?