In the multiverse, different physical regions are so far apart and independent that residents in a given region might not ever even be capable of finding direct evidence that any other regions exist. What do you think about the burden of proof in this situation? Do you side with those who say the theory is impossible to disprove, or impossible to prove? Or do you land somewhere in the middle?
My position is that the theory is impossible to disprove; in fact, there are several good arguments which support the theory, string theory (yes, another theory which remains hard to prove) being one of them (cf. probable Calabi-Yau spaces).
Since we cannot prove or disprove any of these theories, we are in the land of Utopia where anything might be possible, like parallel universes in which different outcomes are played out (butterfly effect etc.). While it may seem tempting to play around with these ideas, I´d prefer some hard evidence to prove or disprove these theories. Given the enormous progress science is making I´m hopeful (if not confident).
If a conjecture regarding reality cannot be tested to prove or disprove its validity, then it currently positions itself as being not worthy of extensive rational discussion. That does not prevent ongoing examination by theorists, and for the proponents of any particular ‘theory’ to defend their pet idea – it is simply that any further discussion at this time is logically pointless – it is just becomes a marketing exercise to attract further advocates in support of an unprovable hypothesis.