Originally Posted by Cranny04
It begins to oxidize
You can prevent this by using an aspirator valve
Or, instead of spending 90 bucks on that, you could pick up a low pressure propane regulator and some hose barb fittings at your local home improvement store for $12 or so. That's how I run the breather on my "cask" ales. It supplies 1/2 a psi of gas, so it's enough to keep a blanket on it, but not enough to really carbonate the beer.
However, both of those require a CO2 bottle, regulator, and keg/cask, so you're pretty much looking at a kegging system right there. Add a real beer engine for $200 or more, and you're behind the curve. So you can see that you're not really looking at a cheap way into the bulk storage world. My advice is to scour ebay / craigslist. Folks are always upgrading or getting out of the hobby and you can pick up a complete kegging set up for cheap.