I agree with Jason Ward's comment about the background of wedding ceremony that happen at that time.
I believe the the Lamp represents faith. And of cousre our faith comes from hearing the Word (Romans 10:17)
"Consequently, faith comes from hearing the message, and the message is heard through the word of Christ."
which makes me to think that the oil is the hearing the message.
People become christians by starting to hear the message. Personally I believe hearing message is different from hearing the word of Christ. Many people comes to church and read bible but don't hear the message, which also don't produce faith in them.
I believe the foolish virgins are the ones who stops hearing the message though they did in the beginning, which of course brought them to new life through grace. This also makes me to think of the parable of sower, third kind of seed were choked by life's worries and etc...
Just my opinion.. :-)