First of all, "Bullet-proof vests" are not exactly bullet proof. There are many styles and ranges of ballistic protection out there. Some are rated for handgun rounds only, ranging all the way up to 30.06 armor piercing round protection. Some are rated for protection for multiple rifle round hits. The higher rated the protection of the plate or vest, the heavier the armor will be to carry.
There are vests that have "soft armor" (which protect against handgun rounds). Then there are vests that have compartments to carry hard armor plates that Velcro into place.
Here is a decent explanation of body armor levels:
Simply put, it has been stated that you should use the level of body armor that would stop a round that your would carry in your defense weapon.
For those that protect their home with an AR-15 or a shotgun with slugs . . . you're looking at investing in at least Level III armor plates and a carrier to attach them to.
Is it practical to don an entire interceptor vest (if you could legally procure one) with armor plates for that bump in the night? Probably not. It wouldn't be easy to put in less than a second or two.
There is a more common sense solution though. Voodoo Tactical makes a "High Mobility ICE Plate Carrier" that can be purchased and shipped free from ebay for around $50 depending on the color you choose.
With side release buckles, your family protector can slip into ballistic protection for his or her vital organs with little effort. Throw a couple magazine pouches on the front and you're good to go for defending your little plot of land from would be thieves, hooligans and wrong-doers.
This vest is not complete without the ballistic armor plates that fit in the front and back secured by Velcro: Both the front and back compartments each take a 10"x12" plate. With this type of vest, you would probably put either a Level III or Level IV plate in the front and back. You're looking at about 15 to 18 lbs depending on the level of protection your choose.
For instance, we came across a vendor on ebay that sells to law abiding citizens (who are NOT felons - as it is illegal for felons to possess body armor), under the name: Vacextar
For $125 you can buy a front and back armor plate that will stop multiple rifle rounds and handgun rounds. That includes M855 5.56MM rounds, 7.62x51MM Ball rounds and 7.62x39MM rounds.
Here is the current auction: http://www.ebay.com/itm/AR500-Body-Armor-CURVED-Plates-Pair-Comfort-Cut-Level-III-10x12-Painted/281038745660?ssPageName=WDVW&rd=1&ih=018&category=102537&cmd=ViewItem
So basically for about $175 you can have a very strong ballistic protective vest for home / self defense. When that bump in the night happens, you might consider grabbing that "easy to put on" plate carrier that you bought shortly after reading this, that protects your upper thoracic cavity and stacks the odds in your favor.
It's something to think about anyway . . . thanks for reading.