Flat out wrong. Many Hypothesis never get beyond the hypothesis stage. Dark matter is one example. It is niether able to be shown to exist or not exist. It may never be able to be proven or disproven. Go ask a real scientist if a hypothesis is unworthy of exploration since we are currently unable to prove it. A HUGE amount of our scientific breakthroughs came looong after the hypothesis, and were unprovable at the time the hypothesis was made. The Atom is one good example.. first theorized in Ancient Greece. In your way of thinking, since it was unprovable, it was useless exploration, and should have been discarded for all time.
Yes, because they're falsified.
Dark matter is one example. It is niether able to be shown to exist or not exist.
Dark matter could be shown false (no theory can ever be proven true). It has many testable empirical implications, and as far as I know, they have all been verified. Here's a site that discusses some of them:
http://www.astro.queensu.ca/~dursi/dm-tutorial/dm1.html
Here's a site that discusses some new proposed tests for dark matter, that would also give us a better idea of what it precisely is:
http://www.lbl.gov/Science-Articles/Archive/Phys-SNAP-dark-energy.html
String theory, on the other hand, is a very good example of modern scientists engaging in non-testable speculation.