Origin is EA's answer to Steam - that is, it's an integrated store and gaming platform, with social bells and whistles thrown in because why not.
Just like Steam, it's rather deeply integrated into some games (most big EA titles from here on, it seems, such as the upcoming Mass Effect 3) which means you can't just get rid of it. It's required to play some of their games, just as Steam was (and is) required to play Half-Life 2, the first flagship title that Valve used to promote Steam, amongst others.
I haven't seen any information on playing Origin games without it installed, apart from one hack for Battlefield 3 (which could easily result in permanent bans as it's against their agreement).
As you also asked for a link to removal instructions in your comment above, you can either use the normal Add/Remove Programs menu from the Control Panel, or have a look at this EA page for manual uninstallation instructions. Do note the Scary Red Text saying:
NOTE: If you remove Origin, you will lose accessibility and playability to any downloaded games and manuals until you reinstall Origin.
So this will not let you play your games without Origin.