Holy crap, on the low-earth orbits, how can they be sure they'll never collide?

Precisely with databases and tracking systems like the one you're looking at. Although I'm sure we're looking at a somewhat smaller version of the real list of every bird and piece of space junk.

There's so MANY of em.

And it's funny to note how many of them are iridium birds.

Do a web search on "iridium flares", that's kind of interesting...