Suspicion
by Jeff
Image text: Fine, walk away. I'm gonna go cry into a pint of Ben&Jerry's Brownie Batter(tm) ice cream [link], then take out my frustration on a variety of great flash games from PopCap Games(r) [link].
In this comic, the main character is having online chats with what appears at first glance to be a woman. However, in requesting that they both "get tested". The woman on the other end of the computer does not pass a CAPTCHA test and is unable to prove she is a human.
This is an internet version of the Turing test. A spambot is a program that send out links (such as in the image text) to simulate an human's writing. This test is called "VK", which stands for Voight-Kampff, which is the machine in Blade Runner which determines human from replicant.
In using the phrase "get tested", the comic is making a pun that refers both to the CAPTCHA test above and the STD test that couples will take to make sure they are physically clean.

September 4th, 2009
And the inclusion of brand names in the alt text is a reference to the advertisements implied by the “and then you mention products you like” bit from the strip, implying that XKCD itself may be an elaborate bot.
September 4th, 2009
No, it’s not. It’s a continuation of the girl/bot’s dialogue from panel 4.
December 2nd, 2010
online chats are nice, you can meet lots of friends and acquintances out there over the internet .:,
January 25th, 2011
.”; I am really thankful to this topic because it really gives great information ;;`
January 29th, 2011
Did two spambots comment on this comic?
August 10th, 2011
How did they miss the “Lisa” at the end of the comic?
Lisa is an AI program/chat-bot written for IRC and later deployed on unsuspecting web chat victims.
@Aaron The irony is fantastic. I’m going to do the same thing after I find something random and totally unrelated!