Dude... that is an EXCELLENT IDEA.
I am going to extend that a bit....
First an admin should have the option to turn these things on or off...
Second... there are a buch of companies where customers always buy certain products over and over again therefor there should be the ability to assign certain products to "reorder products". This way once he logs in it would show these products if he has purchased them in the past.... Also once should be able to set a variable to if a customer purchased the same product "x" times (on different days) it would automatically show that prouduct as something he may want to order again.
It would also be excellent to show additional products he may be interrested in based on what he has purchased in the past... for example... lets say he purchased an HP 4L Laser Printer (I know... thats really old product but the only one that comes to mind)... now based on the fact that he purchased that it should show him the reorder supplies for that product so he has quick and simple access.
If this could be integrated with an auto email engine so it would even notify the customer within "3 months" that for his <product> he can buy these options/reorder supplies it would trigger more return visits/pruchases.
Finally... I do believe there should be an option that this type of data in not only presented once he logs in but also when he just visits the homepage (via cookie).
My god... integrate these ideas (even as a module) and I am positive people that are serious about selling online will purchase it.
Keep up the good work guys...
CH