The email is from someone called "Pams Webster" (yep, that's a giveaway right there) and reads as follows:
etc.Take a look at my photos on Facebook
Hi Phil,
I set up a Facebook Profile where I can post my pictures, videos and events and I want to add you as a friend so you can see it. First, you need to join Facebook! Once you join, you can also create your own profile.
Thanks,
Pams
To join Facebook, please follow the link below:
The email appears to have genuinely been generated by Facebook (all the links it contains point to pages on facebook.com, and it rounds off with "See who else has invited you to join Facebook" and details of several people I know). My first thought was, this is someone who's got the wrong person, so I replied saying sorry, don't believe I know you. Immediately afterwards I realised what "Pams" is an anagram of. Duh.
I'm assuming that a spammer has set up a profile on Facebook and is using it to send out these spurious invites - but to what end? I've tried reporting it as abuse via the Facebook site, but annoyingly they only seem to let you do that if you register to join.