I picked that just as an off-the-top-of-my-head-example, but it isn't exactly an off-the-wall one. Stellar structure and evolution studies are nature enough subjects that any star going nova that shouldn't be doing so would arise intense interest. We pretty much know which ones are about ready to go. If a star like the sun suddenly flew apart, for example, every telescope on the planet capable of studying it would be on it in a matter of hours.

An analogous case is the "blue stragglers", odd stars in globular clusters who seem to have evolved in a totally unexpected and unnatural fashion. There were already crossed fingers in the astronomical community that maybe we had finally found examples of stellar engineering. Unfortunately, further research soon came up with a more conventional explanation for the phenomenon.

My own suspicion, (I can't back this up with any hard numbers) is that life bearing planets are extremely common, and soon we will find one (probably by detecting free O2 in the spectra of a nearby star. As far as intelligent life is concerned, particularly intelligence we could locate, I'm not so optimistic. I believe intelligent life is out there, but I believe it is very rare, in both space and time. We may never find it.

I hope I'm proven wrong, hopefully in my lifetime, but I'm not putting any money on it. If I were dictator, I could not in good conscience authorize funding any SETI programs UNLESS they could be piggy-backed onto other research projects. Pure SETI for SETI's sake is a dream, but it is a wonderful dream.