Limit Per Customer Shops

I Think There Should Be A Way To Limit How Much A Certain User Buys/Sells A Good To You, The Quantity Area Would Add An Area For A Limit So The User Could Only Buy 10 Of The Dirt. Tell Me What You Think!
Example-( On A Sign )

cyberazaz101
1:10
B10:S9
Dirt

No i think what we need, is to where we dont get spammed when people buy stuff. But, put dirt in the chest themselves when you set up shop, therefore limiting amount of items that can be sold to the shop itself

Not sure how this would work, but I don't get why this is needed. Basically if you cap your chest with dirt so that only a certain number can be sold to you or whatever.

I want to know why people want to limit customers from buying their stuff.

Firstly, before anyone else gets here, please don't begin each word with a capital. It makes it hard to read.

I understand how this would work, but why would you need this?

You could make a cap for the amount of items to be sold, just subtract the number you want from 27 (If a single chest), and place that many of any other item into the chest. That way people can only sell you so much. For when people buy from you, just watch how much you put into a chest. But I'm getting the idea you're inferring personal sales.
For that, I like the idea, because people buy me out of stock and hoard it, or resell it without asking me. But it will take a while for it to appear onto EMC, due to EMC's personal updates, and the soon-coming Minecraft 1.6 update. Most suggestions will probably be set back a few months...

Resellers and hoarders, as stated above

How long would the reset period be? What I mean is, after a player buys 10 dirt, how long do they have to wait to buy 10 more dirt? It would be pretty ridiculous to put a lifetime limit on how much someone can buy - you'd lose customers. However, the coding and hardware required for time limits for everything that every player buys/sells wouldn't be worth it in my opinion. I agree with Bunkerllama. Just limit how much you have in the chest at once, and place signs telling how much players should buy/sell. It's not a bad idea, but I think it would be very complicated to implement, and wouldn't add much to the community.

You could also just watch your rupee history and warn any shop "abusers" :3

EMC's default response to this kind of suggestion is usually; - quite right too - just control what and how much you place and give room in your chests.