I think Paul Kemsley and a few others in high positions within the club were known for being liberal with their info. Comolli was also apparently happy to openly discuss transfer targets with anyone who would listen. There were also various other people that had good connections in other ways. Roger Morgan on SO was/is apparently a Daily Mail hack, so would share info before it went to press. Archibald on SO was/is said to have something to do with helping new players find accommodation. I don't think either of them post anything now, which is probably unsurprising when people like me are speculating about who they are.
I think that's one reason why ITK seems to be dead or dying. There's enough info online in various places to be able to identify almost all of the most well known 'ITKs' (especially when they get drunk and reveal things they probably shouldn't), and the increased attention since around 2008 has probably just made it less and less worth it for those that put their own jobs (or jobs of their relatives/friends) at risk.
Then there are those that want the exact opposite. They want to make the most of the attention 'ITKs' get from some people, by trying to make themselves into supposed oracles that have all the answers. Several names spring to mind that constantly troll twitter with their 'info'. They tend to form a wank-circle where they all tweet each other about their made-up or exaggerated info...with each claiming to support whatever the other has said (and therefore creating the illusion of verification).
For me the end result is that the bullshitters have reached such a high profile and online popularity that it has become completely meaningless. Other Spurs forums protect anyone that can produce some tenuous piece of evidence to support their claims (even if it is in reality only a one-off), then from that point on anything they say is treated as gospel. Take 'Wishkah' for example. His only vaguely relevant info was that he worked in finance, and his company apparently had access to some of the club's transactions. Apart from the fact that I'd imagine sharing this info is extremely high-risk, his info was also repetitive...relating to large sums of money being deposited in Spanish bank accounts (none of which ever led anywhere). Within weeks he was posting, coked or pissed up on Friday nights, claiming to know everything from Lennon's secret tattoos, to the tactical plans of the Brazil national team's coaching staff....and people lapped it up.
In summary, ITK ate itself. Too many wankers craving attention have created a sea of bullshit that is impossible to swim in.