To be honest, I don't see how you could possibly do fractional reserve with Bitcoin. By definition fractional reserve is lending more currency than you have. Banks can do this because they are allowed to create the money that they lend. So if I am allowed a 10:1 ratio of lending and reserve, as long as I maintain $1 in my reserve, I'm allowed to lend $10. Those $10 are poofed into existence when the loan is created, though.
As another person mentioned, I think you are confusing lending with reserve banking. A bank (or any entity) is allowed to lend as much money as they want to someone if they are actually lending money that they have. That's not fractional reserve. Fractional reserve creates money. The fraction limits how much money you are allowed to create.
You can't do that with Bitcoin by design. Of course, you can lend money (that you have) with Bitcoin. There is currently no automated way to record that the transaction was a loan as opposed to a payment, but that's true of all currencies. In fact Bitcoin had some plans to implement contracts in the protocol, but I don't think anyone has done it yet.
If I am to opine slightly, I think that Bitcoin's lack of ability to do fractional reserve is probably a mistake. I think it relegates it to a payment method as opposed to a viable currency. The problem with Bitcoin as a currency is the lack of availability. Although it often doesn't look like it, I think the purpose of a currency is to get resources into the hands of people who need resources, but don't have it. With Bitcoin, the currency is a limited resource and those that have it have no particular reason to spread it around. With a more traditional currency, the money supply can grow to match demand. The banks which create the currency have an incentive to loan money because the money that they are loaning is springing into existence at that time -- they aren't loaning their own money. The only thing the banks need to worry about is that on average, the growth produced by the loan is greater than the interest charged. Having a fluid money supply like this allows people who do not have money to get it and reduces inefficiencies (i.e. people being idle because they don't have the resources to produce something).
Having said all that, I have no idea how you could implement fractional reserve in a distributed system and have any protection for horrible abuses. Until that problem is solved, I can't really see a way for this kind of currency to act as a true currency (as opposed to a payment method). If I remember correctly, there was a review of Bitcoin by a prominent economist a few years ago that pointed out this problem.
As another person mentioned, I think you are confusing lending with reserve banking. A bank (or any entity) is allowed to lend as much money as they want to someone if they are actually lending money that they have. That's not fractional reserve. Fractional reserve creates money. The fraction limits how much money you are allowed to create.
You can't do that with Bitcoin by design. Of course, you can lend money (that you have) with Bitcoin. There is currently no automated way to record that the transaction was a loan as opposed to a payment, but that's true of all currencies. In fact Bitcoin had some plans to implement contracts in the protocol, but I don't think anyone has done it yet.
If I am to opine slightly, I think that Bitcoin's lack of ability to do fractional reserve is probably a mistake. I think it relegates it to a payment method as opposed to a viable currency. The problem with Bitcoin as a currency is the lack of availability. Although it often doesn't look like it, I think the purpose of a currency is to get resources into the hands of people who need resources, but don't have it. With Bitcoin, the currency is a limited resource and those that have it have no particular reason to spread it around. With a more traditional currency, the money supply can grow to match demand. The banks which create the currency have an incentive to loan money because the money that they are loaning is springing into existence at that time -- they aren't loaning their own money. The only thing the banks need to worry about is that on average, the growth produced by the loan is greater than the interest charged. Having a fluid money supply like this allows people who do not have money to get it and reduces inefficiencies (i.e. people being idle because they don't have the resources to produce something).
Having said all that, I have no idea how you could implement fractional reserve in a distributed system and have any protection for horrible abuses. Until that problem is solved, I can't really see a way for this kind of currency to act as a true currency (as opposed to a payment method). If I remember correctly, there was a review of Bitcoin by a prominent economist a few years ago that pointed out this problem.