hey i don't believe that trading players back and forth week to week is unfair as long as both teams are getting something out of the trade. Yahoo clearly states that:
"1. All league-related transactions will be executed with the intent of improving the owner's team and/or its standing within the league.
2. No owner may drop or "dump" players from their team for any reason other than improving their own team and/or its standing within the league.
3. No owner will engage in any action that may be deemed to be collusive (two or more owners agreeing to make moves that benefit one team, but not the other).
4. No owner will make any roster moves (including waiver claims, trade proposals, etc.) whose sole purpose is to hamper the play of other owners.
5. No owner will take any action whose purpose is to, in any way, interfere with fair play in a league. "
As long as the trades are fair to both teams, then they are fair trades. You as a commisioner and all other coaches get to decide if these pending trades are fair.