How much coincidence can still be considered "coincidence"?

Is there a limit for coincidence? And how much coincidence can a weekend hold?
Coincidence can be very surprising, even amusing. But I realised that it can also reach a point where it almost appears frightening! When you feel part of a very odd scenario that you know is very unlikely to happen. Almost like a chessman in a match who is the only figure that is not moved around...
How coincidential is it that two people meet. Two people who have nothing to say any more, who live different lives and don't share any thoughts any more. How likely is it that their paths meet at a bus stop at 3 o'clock in the morning? Two people in a city of 7,5 million? And 17,500 bus stops!
The chances to meet random Londoners are quite high, due to that opulent pool of people. But again, how are the odds to find a soul mate on the way to the lavatory? A person who happened to be "in the way" and who turned out to be able to think alike and to read your mind? You discover more commonness with this "random" person then you think it would be possible in one weekend.
It is really random or is it meaningful? Should I stop calling it coincidence and consider it fate? May be there is something like karma and fate is having its through of the dice sometimes. Chess is strategy. Can coincidence be part of a strategy too?
I should take it as an opportunity. Opportunities never keep to any mathematical rules and appear at the strangest moments.