1:1 should theoretically be completely fine if everyone did it, but
unfortunately many people jus grab and go , so i tend to let myself go to about
1:1.5 (but i went over my cursed download/upload limit last month, bloody u.k
companies!!)
public trackers don't require a login account, private trackers (like
demonoid)require an account and track ratio. if you have a low ratio, you can
get banned from the site. generally this is good because it means the community
is usually better at keeping stuff seeded and people don't 'hit&run'.
you are right in general except about demonoid. demonoid isn't really private,
more like a semi-open tracker, ok they use sign-ups and stats get tracked but
everyone can dump torrents from there on index sites like mininova so everyone
can access those torrents. also there are no ratio rules in effect there.
faq ( h ttp://www.demonoid.com/faq.php#st_1 )
"my ratio is getting too low, am i going to be banned?
the site automatically bans users who have low ratios. we give plenty of time
for users to get their ratios up before the automatic banning. however, if you
are receiving the ban warning, it would be best to quickly resolve it."