To some, the premise might not make sense, until one recalls a quote by Confucius, "When you embark on the path of revenge, dig two graves." Well, that's inevitably what happens, as, by pulling the string to send someone to hell, one grave is dug (the one who got sent there) and another is reserved (for the person who employed the Hell Correspondence).
It may seem unfair that after rising from the grave and killing her tormentors, Ai was punished by being conscripted into service as Hell Girl, with the threat of having her parents sent to Hell if she did not comply. Surely she had the right to take revenge after a lifetime of abuse? Of course she did, but that revenge came with a hefty price tag, just like the deal offered by Hell Girl herself. If you can send one person down to Hell in exchange for condemning your own soul to Hell, then logic follows that you can kill hundreds of people in exchange for hundreds of years' worth of service as Hell Girl. The Master of Hell did not seem to blame the villagers for their part in tormenting Ai, but he did not need to, as they were likely being punished themselves in Hell anyway. (If a person can be good their whole life and be condemned to Hell just for sending someone else there [even someone who deserved it], then surely tormenting an innocent child would qualify them for Hell.)
Occurs when you realize that even the most sympathetic of string pullers just did the mystical equivalent of hiring a hitman when they seal the deal with Hell Girl.
Even more so when you realize that those string pullers have at most a few decades before they experience the same horrible suffering as their tormentors for eternity. After the first century in Hell, chances are they will not think that deal was worth it.
Much sadder for those who say that they got no regrets. Being in the flames of inferno for eternity and not able to be with their loved ones in Heaven.
Namiko Todaka, the stuck-up housewife from episode six of the first season, whose posse of Gossipy Hens talked her up as someone who could ruin the lives of anyone unlucky enough to draw her ire. Considering she harassed Keiko Yasuda for catching her in the middle of an affair, sicced a rapist on her, and photographed the whole thing to keep her silent and was willing to risk prosecutionby doing the same to Keiko's daughter Haruka if the poor woman dared to speak about it, it's possible she even used both seduction and her husband's money to get away with ruining her previous victims' lives.
What happened to Kaoruko Kurushima, the actress in the first season who was attacked and fed a chemical that destroyed her voice. It's entirely possible that the thugs who did this to her didn't stop at removing her ability to call for help. It also doesn't help that the setting of this attack is in a dark alleyway at night.
One can imagine all they want but the primary objective was to get rid of the voice.
Just what happens if one person calls the Hell Correspondence to kill everyone in Japan? Let alone the whole world?
Ai Emma can choose not to carry it out. There's got to be a regulation or two with this Hell Correspondence so that sort of thing doesn't happen.
The Hell Correspondence is a one time usage thing. In the Manga, Ai told one of her clients only one can be sent to the realm of torment.
^ Confirmed as of season 4: an episode where two kids are stuck with not one, but FOUR relatives worthy of being sent to Hell, the boy has to ask other people his relatives offended to pitch in because you can only send one person. (Those people say while it might be true, he's using that as an excuse to cover his fear of Hell though.)
After Michiru take Ai's place as the new Hell Girl at the "proper" end of season 4, it might be only a matter of time until she has to banish someone innocent (like the kind-hearted Nurse from the infamous Episode 23 of first season) or someone whose sin didn't naturally warrant entry to Hell (like the outwardly mean but well intentioned teacher from Episode 1 of third season and repetant idol singer from Episode 3 of same season). Considering how she started her "career" with relatively high idealism...
Season 3's credits show Ai standing among almost twenty different Hell Girls before they all disappear. Considering that after Ai vanished at the end of season 2 and the Hell Correspondence was still up and running, just how many Hell Girls overstepped their bounds or otherwise failed at their job and got sent to Hell for it?
Something pointed out by Linkara: After learning beyond a doubt that there is a Hell that evil people go to, couldn't you just take solace in knowing they'll inevitably end up there rather than taking revenge yourself and saving a spot for yourself in hell along with the person you damned?
At least in the first season, many of the situations didn't seem to be ones to get better by waiting (or at least for the person tormented)- remember, there is usually a period of a couple of days when the person with the wara-ningyo waits to see if the tormentor stops, but they never do. This does apply to many cases however.
Hell, the second episode of the first season has a girl access the site to get rid of a stalker, and only ends up pulling the string at the very moment that the stalker is about to kill her with a shovel.
