the danger is thinking youve attained states you really havent, or attaching further to a belief in self. i guess some people who probably already have some sort of mental issue could worsen it, become deranged, i dont know. but with all the meditation books out there one would have to assume that the tradition, as it stands, wouldnt really be too concerned with this.
and on the issue of spirit journeys or other experiences where one talks to ascended masters or gods whatever, just because you run into something "out there" doesnt mean anything they have to say is worth listening to or should be believed. your "spirit guide" could be a dream, imagination, hallucination or maybe some inter dimensional jerk trying to screw with your head... Caveat emptor and remember, dont believe everything you think.
สัพเพ สัตตา สุขีตา โหนตุ
the mountain may be heavy in and of itself, but if you're not trying to carry it it's not heavy to you- Ajaan Suwat