I've been annoyed recently by players that don't observe respect when buying a loot spot. Fortunately this is the exception but it still happens often enough that it's frustrating.
If you make a trade to pick up a loot spot that you see posted in the trade tab PLEASE be ready to play - this is especially true when the player making the offer specifies that they would like a 'fast general'. Saying that when offering the spot makes it clear that for some reason time is important to the player making the offer. I have waited and waited for the invite to even be accepted to be told 'oh sorry - I need to finish my other loot spot first or I need to wait for my general to return'. Why did you accept when you were not able to play?!?!? Most recently I happened to be on a Premium day that was rapidly running out. I wasn't pleased.
Most players thank goodness know better or put information in their offers such as "I'm ready to finish but you don't have to be" which is very helpful and very clear. But if the player requests a fast general they are also telling you something -- e.g. Hurry Please!
Since after an invite is sent the offering player is quite stuck I would ask that the accepting players be ready to go immediately or else whisper and explain and ask if your situation is ok. Don't let the adventure owner find out after they sent an invite that you have some other things to do first.
*addendum*
It can happen quite by mistake that you buy a LS and had forgotten you are already tied up because someone else had problems. If so, offer to use arrows or add more to the purchase price or something in the way of an apology. I have found that sometimes it is quite by accident and wasn't greed. I wanted to point out the other possibility.