Now, I'd like to emphasize that there is some evidence- I doubt anyone is going to go running off claiming that we've definitely spotted aliens. But I think it's likely- sort of.
I think our understanding of what constitutes life is far too limited. Alien life would be- well, truly alien. We would see something completely unheard of. Plasmas living in a star. EM standing waves trapped by the gravity of a black hole's event horizon. Self-reproducing turbulence patterns in a liquid atmosphere. That's the sorta shit that gets my imagination firing.