i believe that during Yoganandas' time here on earth kundalini and raising the energy in the spine was considered dangerous by many people.
Yogananda emphasized the safe use of Kundalini safe use thru kriya yoga and the guidance of a guru who could help the devotee avoid the pitfalls of misusing such a technique.
I was thinking about this, I have been reading here and there that awakening kundalini can be dangerous for some, depending on a lot of factors.
This would indicate to me that it would be fairly important that kriya should be given individualized, from a master, like Lahiri did. Seeing as how that doesn't seem feasible here in the west, SRF will grant access to the lessons via a phone call.
I'm not convinced that is safe for some.