Blood transfusions have the potential to pass on infectious diseases like hepatitis and AIDS. The chances of this are much less now with improved ways to screen blood products.
Blood loss is possible with any operation. It isn't a standard part of treatment for all hip fractures. Some types of hip fractures are more likely to need blood replacement. There's more blood loss with unstable, displaced fractures.
In a recent study of 537 patients treated for hip fracture the patients who got blood needed about the same number of units. Outcome and death does not seem to be linked with blood loss.