Marketmakers and BP

[garytrade2win]

Hi

just trying to get my head around the idea of marketmakers

given BPs issues at the moment - say no end customers actually want to but
any of the stock

you have a 100 and want to sell - your local broker (phone or web site) will
still give you a price as they deal with a market maker who is under an obligation (the bit i'm not 100% on) to offer a price and accept your trade if you commit to it

if they are obligated who decides this and what advantage is there for them for this ?

do they just treat cases like BP as the price they pay compared to the other more viable stocks ?

BP picked as an example - company X could be substituted

thanks

update - tried the google - found this

http://www.btforex.com/index.php?option=com_content&view=article&id=141&Itemid=94

Market maker: A financial institution or individual making consistent buy and sell quotations in a selection currencies. A market maker must hold or have ready access to the amounts quoted, that is carry an inventory.

looks risky to me - they must have to hold some large supplies of some "questionable investments" at times

update - are there only market makers for say the FTSE 100 or main Currencies or does it apply to all stocks and currencies

thanks again !