inviting people to private bittorrent trackers always comes with a certain risk. depending on the tracker you might get a warning, get disabled or even the whole invite tree may lose their accounts.
why do people take that risk? why does one put the future of his own account into the hand of others?
there are two main factors that motivates people to do or not to do something hence to make a decision. one is avoidance of negative consequences, the other is personal benefit.
you can divide inviters into three main groups:
their motivation is really simple to explain. they invite people in exchange for invites or accounts to other sites. this benefit outbalances all negative consequences for them. disabled accounts, hiding from staff, inviting cheaters, getting banned etc. aren't a problem for them. as long as the trade partner delivers the promised good, they really don't care.
2. the public giveaways
people who make public giveaways do it to get recognition and a reputation in invite forums. they consciously break tracker rules as well and don't care much about who they invite either. their benefits are rep points and (from their point of view) a better chance to be considered in their next request for invites or a giveaway they take part in. because of this somehow delayed expected exchange the benefit isn't an instant one. the proportion of negative consequences and benefit is more balanced. that's why they ask for screenshots and other proofs from the strangers they invite.
group one and two have one thing in common. they are both looking for invites to other sites. this leads us two group three. it's hard to find a name for them. let's call them:
3. the ones who have what they need.
this group of bittorrent users have the weakest motivation of them all. they're not looking for invites to other trackers. most are satisfied and often long time members of the best sites. their only benefit is to bring someone who they like and trust to the site. you might call it a favour without something in return. the risk they are willing to take is much higher than their personal benefit. that's why they'd never invite strangers or people they don't know and trust. invites are given in private and as a gift without any need for publicity. they'd rather keep their invites forever than risk their accounts with a bad invitee. the possible negative consquences clearly overrule the personal benefits. that's why they hardly invite people (anymore).
of course this is stereotyped thinking. we're all individuals. the boundaries are blurred. i just explained the main motivations to invite people from my point of view based on the observation i made over the years.