There is a lively debate on many forums about the challenges posed by undesired cross-tier trades, possibly due to the excess of T3 caused by event buildings. In my experience, a select number of players post most of the undesired cross-tier trades, which then stay on my trade list until they expire, clogging my trader. I don't like this. One solution would be to add a very small fee in coins to post a trade. Perhaps something along the lines of 0.1 percent of the MH coin capacity. So for example a new player with a MH coin capacity of 68000 would pay 68 coins per trade. This fee should be small enough that people are not discouraged from posting trades that they have a reasonable anticipation will be taken, but significant enough that there is some deterrent to posting trades that are exceedingly unlikely to be accepted. Of course there are some problems with this, like making it more expensive for people to do pass-through trades, but if the fee is small I don't think it will substantially discourage people from posting trades they expect will be taken. I know adding a fee (essentially a tax) is never popular, but I see this tax as sort of like a "sin" tax like the tax on cigarettes, because mainly it will affect those who post large numbers of trades that other people don't want. Edit to add: A related idea, that could be used by itself or in combination, would be to shorten the time window during which trades are valid. I think 2 days should be the maximum time. I rarely have to wait more than a day or two for any reasonable trade I post to be accepted, and even if it did expire I could simply post it again.