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My lawn (1/5 acre) is all lumpy. Would it be better to find some fill dirt and fill it in, or till it all up and try to even it out that way?

I'm in the Willamette Valley in Oregon.

Are you fans of Minecraft? I always felt that it was the digital equivalent to all the fun I had with legos at a kid.

eventually a cartel of miners has 51% of the mining power and thus controls the price of BTC

Mining has little to do with the price. If a cartel of miners had 51% of the mining power and intended to do wrong with it, then Bitcoin would be finished. But just because someone or a group of people might control 51% of the network doesn't mean they could possibly control what the price does. And the incentive would be to mine with that 51%, not use it for nefarious purposes anyway.

Your second point isn't really possible. The only way to drive the price of bitcoin down is to sell bitcoins. And you can only sell bitcoins if you buy them first. And if you buy them, you drive the price up. Fiat may be unlimited, but bitcoins are not, so there's only so much an entity could do to drive the price down, and it would only work for a limited amount of time.

I just mean that if it happens once, and there isn't a good solution put in place to prevent it from happening again, then people will naturally assume it is going to happen again.

You can mine with your computer, but it is incredibly inefficient now. Even a good video card might mine you $0.10 worth over the course of a year. There is dedicated mining hardware that attaches to computers (usually via USB), and you can mine much faster with those. It's still a bit of a losing game at this point though, with how far the price has dropped.