Accounts suspended for exploiting the economy

Dear support my guild mates and friends have been accused by Blizzard for exploiting the economy and have had their account suspended for 3 days for investigation. I really do not know what have lead to this and if it is an automatic detection system put in placed. He was trying to raised money for his epic mount and have borrowed money from a guild mate to attained it as had some money in goods in the AH.

He finally raised enough gold and kindly returned it back to person he borrowed it from. He sent 900g to them and his flat mate sent 500g to them. Both of these account have been suspended for the same reason.

We did not do the transfer via player 2 player as the person who they borrowed the gold from was not available at the time.

The account in question is Teamo and Takiuk both are flat mates. I have read on the internet that the reason for exploiting the economy tends to be related to gold selling but there is no clear cutt answer. Can you please give us an indication of whats wrong so this will not happen again and the players can happy adventuring the WOW game. They have manage to attain enough gold for the first epic mount and is trying very hard to get money for the second mount.

I really do not know what your reason is are we not allow to sell a lot of things in AH to raise gold? are we not allowed to borrow gold from friends in game? They have both emailed the 'WoWAccountAdmin@blizzard.com' to get an answer.

Account: Teamo and Takiuk both are in Scarlet Crusade server

Really hope someone can help.