[Scorpious]

Definite minimum level and age requirements should be implemented if this ever happened. Humanity level should not really matter. Some borg with .5 humanity left may want to sell .4 of his humanity. Any amount for any price you want with a minimum implemented. If the borgs want humanity back they will pay the arm and a leg "LOL" to get it.

No newbies (what would stop me from going to another computer somewhere and creating multis and helping out people I know by selling them humanity for a song).
Level: 20+ at least.
Age: 90 to 120 days. Must be active for at least 2 months otherwise inactives can login, sell to their buddy/buddies and be inactive again. Why should they care, they are inactive.
No similar IP addresses either.

Also should have a minimum price for each .1 of humanity sold. Make the parties send cash back to each other if they want it for nothing or next to nothing. Gives others a chance to mug them for it.