Not wanting to run a relay is up there with things like not running an open Wifi access point, or not leaving your door unlocked. Willingly offering your personal internet address to complete strangers with no interest in your well-being is insane. It can only end badly.

Like the OP of this story, if you do not understand the risks of TOR, you should definitely not be using it.

I always thought this is being a nice person.

No, it isn't. An open WiFi will most likely not be used by someone trying to do something that might be either illegal or piss off some powerful entity whereas a Tor node will be just that.

So you need to weigh whether or not you want to do this a bit more carefully than you would if you left your WiFi open. On top of that an open WiFi will likely not get you blocked by default from a ton of other online services but running a Tor node will get you blocked from plenty of services in a hurry.

This because Tor for most regular website equates to 'people that we have already gotten rid of using other means' or 'people that are up to no good'.

The open wifi requires you to log in with credentials that are linked to a credit card and name. So any weird activity would be correlated to that login. Of course someone could use a stolen credit card, but at a minimum, "bad" traffic would be correlated to that account, not the open wifi that Comcast is allowing to take up your bandwidth.

Yes, I know what you're going to say - "but then a lot less people will be willing to use it!". Maybe. Or maybe not. Maybe it becomes something that's just "normal" and you don't think about it, just like seeding torrents. Then if it's something people don't think about, and it makes running Tor "more acceptable", I think even more people will use it.

Currently we're in the situation where potentially a large percentage of the relays are run by NSA/FBI. If millions of people would be relays, then that would either be much harder for them to pull off, or much more expensive. Either way, a better outcome.

Nope: http://bitthief.ethz.ch/

Bittorrent is just a good example of the "defaults matter" guideline.

By the way, I don't think relays are the problem. Exit nodes are, and you can't force everyone to run one, since it would literally lead to detentions and even prison sentences.