There is definitely some advantages to running it yourself. For example, if you have 14 racks in a basement and you don't go all technical and professional, you could cool the spce with an exhaust fan and a floor air conditioner. The 7000 cfm fan to cool it, would cost $1 to $2 per day. While it might not be the best setup int he world it could work.
On 14 racks depending on how much bandwidth you are using, you could run dual DS3's instead of fiber. Let's face it, data cetners expect you only to use less than a meg per box. The average data center rack consumes between 10 - 15 mbps per month. I know that is between 140 mbps - 210 mbps that is a lot of DS3 lines. The thing is, you can get AT&T , Charter, or Comcast to run you a ethernet up to 1 gbps for under $20 per meg even in remote areas. I know, I looked into it.
If your not trying to run a enterprise level options, you can keep costs much lower. You buy a $500.00 durarack and there is no $300.00 - 800.00/month in rack fees. You have taken it so your paying bandwidth and electric only.
While I wouldn't recommend it, it is possible and could be done cost effectively.