I drive way slower if there's the police watching. So, sure.

No. Unless the "event" notices you watching.

According to the double-slit test it surely does

According to Heisenberg it does.

Semantics and philosophical fluff.

Definitely, I instantly stop masterbating when I realise I'm being observed.

Depends on both context and perspective...

According to quantum physics it does, so far!

Everyone will have a different perception

Yes. There it goes again...

Reminds me of the old tree falling in the forest query.

Without a whole quasi scientific pseudo elaboration on your question, I'll just say, no, I do not think observation alters an event. However, multiple observations will render multiple accounts of the event many of which will likely differ. So, in that regard, I suppose you could argue that, yes, observation altered the event.

Absolutely. Double slit experiment proves it.

Without being overly technical, the answer in my opinion is yes. Heisenberg proved on a quantum mechanical level that it is impossible to measure something without changing it. Think of it like tasting bourbon. If you sample the bourbon from the glass, you have changed the glass of bourbon. Philosophers have extrapolated Heisenberg to larger systems in the universe, like glasses of bourbon. If you are interviewed by a newspaper reporter who asks probing questions, would your outlook possibly be changed by the introspection required to answer them???

[en.wikipedia.org]

I think it really depends on the event in question. If it is people driven, and the people don't want to be seen then yes, it could stop them from doing whatever it is. If those involved want to be seen, then no... I mean that's what they are after, being observed.

Now in non human events, nature... say lightening striking... it will strike regardless of observed or not. If a tree is going to fall, it will fall, witnessed or not.

In the case of quantum mechanics, it sure does.

It is well established that human behavior is altered when the subject knows he is being observed. Neither will my dog steal food from a toddler while I am watching. In the physical universe I would say no, except that I am led to believe that electrons do behave differently when observed. I am too stupid to understand quantum theory. I accept nothing on faith alone, so I can only pass on the "double-slit" experiment without my personal attestation. [highexistence.com]

That's a No/Yes question..... If you observe a stone then nothing gets altered. If you observe an atomic particule then the answer is yes....the good stuff is why..... To observe anything light is mandatory (try to see your hand in a pitch black room). If the system under observation is bigger than photons (light) then no alterations. If the system under observation is an electron then throwing light at them knock them off their path, which clearly interfere with it. The paradox gets missunderstood and things get a bit more confusing when the infamous cat enter into the picture but that's another story. Good question !!!!

For us, yes. The actual event, I don't think so. Especially since every event we're seeing milliseconds after it actually happened.

Quantum Mechanics says yes. And I believe there is a cat involved with this question as well, though I can't say if it's alive or dead.

Yes.

It certainly can.

Yes it does.

Too many questions.

I think our culture and our conceptions have a lot to do with what and how we observe, which alters our interpretation of events.

Imagine some one who knows what a duck is but has never seen a rabbit. What would they observe looking at this picture?

My favorite quote on the subject, most often attributed to Richard Feynman:
"If you think you understand quantum mechanics, you don't understand quantum mechanics."