I have the feeling they used to date during AWKIF...
On the thank-you's Josh says "Nichole W, experiencing life with you is the greatest gift. Thank you for being who you are. I love you" and Hayley says "Neil, you inspire me and I love you, my prince"
And Josh's middle name is Neil and Hayley's is Nichole.
But then I think something happened because on RIOT! Josh said "Hayley, you're simply my best friend and I love you."
and there are lots of pictures where the CAN'T deny that the were dating
That's my theory anyway