I think that passive or friendly mobs should be allowed in the main world because in 1.4 the carrot on a stick is only used for pigs and i dont think people will risk their lives on a pig in mining world for riding a pig. Next is that ive heard so many people say i wish i had a egg farm and ive heard people say why do they use /butcher i had 10k plus chickens or whatever. I think that main world should be a no /butcher world and everyone has a limit on how many animals are in a certain radius so like 1000 in 2k blocks or something so it doesnt cause alot of lag. And a Mod or Game Admin Or a staff can come kill the animals. By New page on the fourms animal lag reporting or something like that where you report where animal lag is Comment Rate Disagree Agree Whatever!
I honestly wish mobs were in Main-World again. Way back around the time I started, mobs were in the Main-World, but sadly, they were removed due to lag. However, the Aether still has passive mobs! The Pilot rank cost $20,000, and it is well worth it! Mobs will probably never be in Main-World again, but my advice to you would be get Pilot!
Sadly due to the way mobs are coded in minecraft they create large amounts of lag. I think everyove would like to see there return to the mainworld, but it just can't happen right now :/
