It's an interesting theory but I feel like it doesn't reflect the reality.
If galaxy was indeed teeming with rocks containing some sort of microbes than where did they all come from? It'll take an enormous amount of effort to populate an enormous amount of rocks and scatter them across the galaxy. I wouldn't presume that Protozoa would appear on asteroids just by itself. For this mechanism to work there would have to be millions or even billions of such rocks for every star system to ensure that at least a couple of them land on a ripe planet and some of the microbes survive the impact. Most of these rocks would end up falling into a star or a massive gas giant. And we have to think in terms of billions of years here. So these populated asteroids would have to keep falling on a potential life-supporting planet for a couple billions of years until it indeed become habitable.
Ok, even if this mechanism of fertilizing planets was indeed functional as you suggest, we still don't see any evidence of intelligent life out there in our galaxy. Surely, out of billions of planets and billions of years time there would emerge at least a couple of civilizations capable of colonizing a significant part of our galaxy. There's certainly a slim possibility that we may be the first of such civilizations, but I'd be surprised to find out that humanity is THE smartest and most reasonable civilization out of billions others that our galaxy was capable to produce so far.
If Venus wasn't hit with something massive why the weird backwards and slow rotation that no other planet has?
I feel like even if Venus had Earth-like atmosphere it'll still be hard for life to endure the 121-day long "day" and "night" where temperature would go from like 250°C to -250°C (numbers from the top of my head). Maybe only on poles there would be possible for water to stay in liquid form for long enough so that life could emerge.
Never heard of Couchsurfing and I'm quite shocked this idea was able to captivate a considerable amount of people. It all seems terrible to me. Invite a bunch of strangers to hang out in your house? What a terrible idea! Sure, not all people are morons or psychos but there are such people out there. And only one is all it takes to end or completely ruin your life. Risk a life to be able to hear a bunch of bullshit what some idiot has to say is totally not worth it imo. If you want to talk to an idiot - you can find plenty of them on Facebook or Twitter. At least it's safe. And for the real life communications just hang out with your family, classmates, coworkers or even neighbors. There are a thousand people that you know and have some sort of relation to. If you wanna date - use tinder or something.
Be careful out there, if not for yourself but for those, who love you and care for you!
Ok, even if this mechanism of fertilizing planets was indeed functional as you suggest, we still don't see any evidence of intelligent life out there in our galaxy. Surely, out of billions of planets and billions of years time there would emerge at least a couple of civilizations capable of colonizing a significant part of our galaxy. There's certainly a slim possibility that we may be the first of such civilizations, but I'd be surprised to find out that humanity is THE smartest and most reasonable civilization out of billions others that our galaxy was capable to produce so far.