Yup,
eliquid does catch fire when heated up enough and they're exposed to enough oxygen.
Happened to me the other day while showing off the vapor produced by my Phoenix
rba with the top cap off.
Heard a little "thump" sound and no more vapor.
Upon closer inspection, I noticed the very slight, nearly invisible flame, like when you light alcohol on fire
(which is what makes alcohol fires even more dangerous).
Just be careful when test firing and tweaking. Never test fire it while holding it under your face! (don't ask, lol)