Sorry about that I will try to get do better in this edit but well there seems to be no clear reason other than a really messed up relationship!
It all seems to have started when Jameson bought the Bugle and used it to fight against crime -
For decades Jameson used his newspaper to crusade in support of civil rights for minority groups and against organized crime. His efforts in the latter area led to his nearly being killed on orders of the Kingpin of Crime. However, Jameson's brush with death did not frightened him away from publishing attacks on and exposes of organized crime
This just set him up to hate Spiderman when he moved from >! entertainment to crime fighting
Spider-Man first came to public attention as an entertainer who used his powers to perform on television and stage. But when Spider-Man captured a burglar, Jameson became outraged that this masked entertainer would use his dangerous powers to take the law into his own hands. Jameson began speaking out against Spider-Man in his lectures and newspaper editorials. Jameson raised enough public doubt about the mysterious Spider-Man's motivations that Spider-Man was blacklisted virtually overnight by the entertainment industry.
Managing to save the younger Jameson, the elder Jameson then publicly accused Spider-Man of sabotaging the capsule in order to save it as a publicity stunt, and denounced his illegal break-in at the military base. As a result, Spider-Man became an outlaw. Shortly after this, he hired a young photographer named Peter Parker who sold him pictures of Spider-Man's fight with the Vulture, never realizing that Parker and Spider-Man were the same person.
Then there is the fact that
At least once, Jameson has come to the realization that he detests Spider-Man for being the self-sacrificing hero Jameson hates himself for not being
This all explains why he hates Spidey and as far as I can see the logic on Spideys half of the relationship does not make half as much sense. After Jamerson has ruined his career
Jameson began speaking out against Spider-Man in his lectures and newspaper editorials. Jameson raised enough public doubt about the mysterious Spider-Man's motivations that Spider-Man was blacklisted virtually overnight by the entertainment industry.
and makes him a wanted fugitive he goes and works for the Bugle.
As a result, Spider-Man became an outlaw. Shortly after this, he hired a young photographer named Peter Parker who sold him pictures of Spider-Man's fight with the Vulture, never realizing that Parker and Spider-Man were the same person.
Saves his life (twice) -
Jonah yelled at Peter, causing Peter to snap and yell back, stating that his photographs kept the Bugle selling while Jonah raked in the profits and paid Peter a pittance. This caused Jonah to yell at Peter again, but he stopped short and had a heart attack. Peter gave Jonah CPR until the paramedics arrived, who rushed Jonah to the hospital.
Then there was later when -
Peter, as Spider-Man, paid a visit, and accidentally let slip that the Daily Bugle has sold to Dexter Bennett, which caused Jonah to have another heart attack, forcing Spidey to once again give him CPR. Jonah did not, surprisingly, blame Spider-Man but instead he just kept on muttering, "Dexter Bennett".
The only reason I can see for Spider-man to wanting to work for Jamerson, Beyond the idea of keeping an eye on him and what new way he is planning to get Spider-man was because in some strange way he found it entertaining?
I mean in everything I have seen Spider-man has had a strange sense of humour and the result was in the end this -
When Spider-Man unmasked to reveal himself to be Peter Parker, Jameson fainted dead away at the realization that the man he'd been calling a menace had been on his payroll for years.
Then there was this moment -
Jameson had always believed that between him and Peter Parker was a bond of trust and he had always regarded him as another son, the "last honest man" in the world; he had always bought his photos, even the ones that were poor, to help him in a discreet manner. After the public confession of Peter, he felt so betrayed and humiliated that it shattered their bond and he became determined to make Peter "pay", despite Parker (as enforcer) and Jameson both actively supporting the Super-human Registration Act.
Spider-man - Surprise! (just me being funny!)
But once again things get complicated >!After Dr Oc make Jamerson like Spider-man -
Jameson later asked Spider-Man to oversee the execution of Alistair Smythe, the person who killed his wife, at the Raft in order to ensure that he does not break free. Smythe, indeed, tried to escape, but Otto killed him at the behest of Jameson. Spider-Man then forced Jameson into giving him the Raft, which caused Jameson to hate him once more.
and yet in strange ways he keeps Spider-man safe -
Jonah aims the camera into Spidey and announces that now has come the time to reveal the face behind the mask of Spider-Man. Of course, his ego wouldn't allow this to actually happen, and he remained in the center of the camera's shot, blocking the view of Peter's face.
So in the end it is one complicated and messed up relationship!
It's complicated (spoilers ahead) - http://marvel.wikia.com/wiki/John_Jonah_Jameson_(Earth-616)