Espada9 said:he tested positive for receiving a blood transfusion from another person. Why he would actually do this I could not imagine. There would be no advantage to this and the risk is as you could imagine could lead to a fatal disease.
Thousands of blood transfusions are given every day in hospitals etc. The current state of testing for blood-borne viral infections is such that the risk is very, very small.
As stated by others, the benefit of using someone else's blood rather than your own is that (1) it is fresh blood, not stored, and so less damaged cells; (2) you don't have to go through the problem of reduced performance following a donation.
However, Epo would be easier and safer!