I don't know how possible this will be, but it doesn't sound that complicated:
Right now, if 2 things add the same recipe to an IC2 machine (the macerator is notorious for this), Minecraft will crash with a rather unhelpful java.lang.RuntimeException: ambiguous recipe error. Just Googling for it shows it's not a rare thing to occure: [google]ic2 ambiguous recipe error[/google]. The only information that the error returns is the recipe that is duplicated, without even directly specifying which mod is adding either of them. Whether it is possible to log which mods add which recipes without impacting load times I guess might help this somewhat, but most of the time the crash returns the stack trace of the 2nd mod adding the recipe, so you can at least complain to that particular dev if necessary. The main issue with this system is that surely if the recipe already exists, rather than crashing and getting all upset (but without actually blaming any mod, or a more helpful suggestion like Greg might do explaining what is happening and why it's not an IC2's fault), why doesn't it just skip over adding the recipe a second time and putting a fatal entry in the log that x mod tried to add a recipe that has already been added by another mod?
If the only change is to improve the crash message, can the pretty similar ambiguous recipe error for when an item has been added to be processed twice but with different outputs be improved too please? 
