If your deck has a high concentration of changelings then these are worth considering, but if you're only running ~20 cards or less that they can help ramp then I would avoid them unless they come with sweet utility like Goblin Warchief
Meow, thats what I call value
Im eyeing it up for Liesa, actually, where I play Manascape Refractor and Cabal Coffers
The spell that does so, Awaken the Blood Avatar, serves as an Edict for all opponents, however, and the Avatar himself can quickly burn down the whole table with its attacks, making the sacrifice worth it in a dedicated deck
Unfortunately theres no way to fix this, short of making token copies of stuff we steal
Typical limits are 2-5 items per person per day, though this varies by location and card availability