Not sure if this is the right place for this or if it has already been mentioned but if you have a contact that has a instant messenger/service entry you do not get the option to then email them using that instant messenger address unless you manually add that instant messenger address as their email address.

For example, I have a contact that when I click on their name I can see their phone number, address etc and I can see which services I can instant messenger them using (gtalk/skype/msn etc) but I have no option to just email them instead of sending an instant message.