In defense of the 1 DEC listing fee:

• as mentioned, it will reduce network congestion and spamming
• it creates another DEC sink, which in theory should make DEC more valuable
• it would overall raise the cost of renting as everyone and every bot will need to raise the rental fees
  -- if rental fees go up, more people will buy cards, which means the value of cards should go up (ceteras peribas)
  --- this is only true if demand stays constant

However, won't the 1 DEC listing fee kill the market for low value cards? If the overall mechanism causes card prices to increase, it's going to make it more expensive to fill in the gaps for everyone's decks. Charging 0.1 DEC (or maybe even 0.01 DEC) may have the same effect of reducing rental spam without causing too much of a shock to the rental market for cards that don't command high rental fees.