There must be something very wrong with LoL's metagame if carriers are able to farm freely.
But I agree, with you go back to base with 4k gold is better to buy a Infinity Edge than Zeals.
And if my opponents arent complete retardeds, they will remove my stacks. It's not a very good logic.
Stack items have a terrible
stat per gold ratio when you buy them. If I can get kills with those items, it means that my opponents suck... so why not to buy a good item and defeat them?
If my opponents are worse than me, I don't need those items to defeat them; if they are better than me, I won't get stacks. It's a lose/lose situation IMO.
Attack Speed and Critical Chance have better
damage per gold ratio than Attack Damage, even in a "naked" champion. But I agree, Youmuu's is awesome on Yi.