Cholesterol is mainly used for conferring  flexibility to the liposomes. So according to me, the only threat conferred by cholesterol obtained from animal sources can be  that the cholesterol  being contaminated from undesirable microbial flora  which may lead to confer instability to liposomal structure leading to drug leakage and unstable liposome formation.

Thanks Ali and Harita

As per regulatory guidance one can not use raw material from animal origin, particularly in parenteral formulations. It causes Bovine spongiform encephalopathy (BSE) a fatal neurodegenerative disease (encephalopathy) in cattle that can be easily transmitted to humans. Liposomes are mainly used for parenteral applications. In scientific discussion of Caelyx (doxorubicin Liposome), it is clearly written-"To ensure that there is no risk of transmission of bovine spongiform encephalopathy linked to the use of cholesterol, the applicant provided information on the source of this material.." It indicates cholesterol from animal source is a potential threat!

Thanks Sopan