You meet someone in-world. They are hot. You flirt. There seems to be an intense connection. Maybe you hook up. Maybe you don't. But you soon find yourself thinking more and more frequently about the object of your affections. At some point an invisible switch is thrown and you begin to experience intense emotions and mood swings that are overpowering at times: Exuberance if it seems they share your desire; a terrible ache if you feel it is unrequited. As a matter of fact, the more uncertainly you have, the stronger the obtrusive thoughts become. The overwhelming feelings don't only color your virtual life, but bleed into your offline world. Although it occasionally transitions to a stable mutual love, we all know how the story usually ends, right? Not well.
There are two books I recommend that explain the psychological and biological factors behind this kind of chaotic scenario.
Although understanding limerence doesn't make one immune, it can provide a little light to help weather the storm, both for the limerent and the object of their infatuation.

My point isn't that everyone should swear off the joys of flirting, emotional connection, lusty interludes, tingly crushes and the ten thousand and one pleasures of virtual eroticism. Only that we will likely save ourselves and our loved ones a great deal of pain if we go in with eyes wide open to the underlying dynamics. And if you are especially vulnerable to limerence, it may be best to at least take a breather and work on the related issues when you're not in the middle of an outbreak.
Anyway, I'll continue to lay out the Botgirl spin on the topic in future posts. I have a feeling this will be another controversial subject and I look forward to the possibility of an interesting comment thread.