Scams on facebook/bebo etc

I have a rarely used facebook and bebo and others entries. I sometimes get emails like this below. I don't know exactly what the scam is. (sexual?) but who would write to a complete stranger of indeterminate sex like this?

"Hello,
it give me a great pleassure to write you after viewing your profile which really interest me to have communication with you if you will have the desire with me so that we can get to know each other and see what happened in future.
i will be very happy if you can write me through my email for easiest communication.
my email is @yahoo.com
i will be waiting to hear from you.
have a blessed day.
helen"