I actually keep in touch with a few of my ex's in the sense that we are facebook friends and send each other Happy Birthdays with the occasional thumbs up for an extremely awesome post. I think the problem with talking about your ex is that time warps the thoughts and feelings that you had into fuzzyness. At the end of the day you spent a chunk of your life with that person so it can't have been all bad and if you managed to come to the end amicably it means you both took what you needed from the relationship and were both ready to move on.
I'd like to say to most of my ex's - thank you for putting up with me and count yourselves lucky you don't have to put up with the old woman version as I seem to be getting worse with ripening. Thank you for listening, for giving me your advice, for calming me down and keeping me going. For being my strength at a time when I had none and for helping me to believe in myself when I never thought I could.