When you take away an item a girl likes she loses only some happiness, but when you give it to her she gets several other stat bonuses (most notably a +1 to Obedience). This means it's possible to max Obedience by buying a cheap item she likes (like a dagger), and pass it multiple times between the player and the girl.
Something similar happens with several traits (if I remember correctly, Small Boobs, Nerd, all the traits that increase/decrease enjoyment cause this, and probably more). With an item that grants one of those traits it's possible to max stats by repeatedly equipping and unequipping the item.
However I've read that the Core Traits file is going to be converted to XML, if that means the stats changes traits provide will be included in the Core Traits XML (like the item XMLs) then fixing this now is not worth it.
Is it possible for Infinite="true" items to appear only once in the shop? It's annoying when stuff like bauble necklace shows up 4-5 times.