In an effort to make more efficient use of resources, the world has started to move towards sharing resources. There were attempts to share things such as bicycles, cars, basketballs, umbrellas, etc.!
There have also been projects in the crypto space to share computing resources such as hard disk space, processing power, GPU resources, Internet bandwidth, etc. These projects encourage users to share by rewarding them usually in the form of tokens that can be exchanged for other goods and services, or even cash.
If everyone behaved rationally and legally, this would be fine. However, we live in a world where there are always people with bad intentions and abuse the trust of others. Using the sharing of Internet bandwidth as an example, you might be willing to share your bandwidth because you have a excess bandwidth that you do not utilise and you thought of making a quick buck. What if the person who hopped on your Internet connection decided to surf to a child pornography site? The IP logged on the site will belong to you, and even if you are able to prove your innocence subsequently, there will probably be a long investigation before that happens.
You might be a nice, caring soul who cares for the world, but beware the evildoers who have every intention of taking advantage of you!