Nothing. Since BTC is deflationary by design you just increase it a little bit. Since modern economics really dislikes deflation at any rate it does not matter how much deflationary it is.

Increased value for the existing coins I would assume. There are plenty of cases of people "losing" or effectively destroying large amounts of bitcoins. BTC is designed to support smaller and smaller portions of a coin to handle the scarcity iirc.

Deflation. The value of the rest of the existing stock of BitCoins goes up slightly, assuming no net change in the demand for them.

Are you trolling? What the actual fuck are people thinking when they post comments like this? Disregarding that you can spend small fractions of bitcoins, what happens when you lose a dollar bill? inb4 "Oh don't worry about it because the bank just makes money out of thin air"

It's not hard to create a new coin as well. For example Litecoins are divisible a hundred more times than Bitcoins with a cap four times larger. If we need more, make more.

You can burn fiat cash, and fire gold bars into space. What are the consequences of those actions? Other coins are presumably worth more because there are now fewer of them.

I would think in a 'tulip bulb' bubble supply is not entirely the important variable. Growing demand would be the driving force behind valuation. Losing a few coins would matter not at all. Maybe even a lot of coins.

Sure, you can just print more cash. With gold bars the gold would become (I assume) more valuable. But at what point does it seesaw and there isn't enough of it to be of any value? I guess with BTC there are satoshi's.