When adding vocabulary from multiple lists, like Chinesepod lessons, can anyone tell me how duplicate words are treated? For example, 要is a word/character that is found in many lessons. If I consistently choose to add all vocabulary from a lesson, am I increasing the frequency of 要, or does Skritter recognize it has been added previously and disregard it. 多谢！

It only gets added once. If you go to "Vocabulary" and browse a list, you can see whether each item has been added or not by looking at the right-hand side of the list.

For example, take a look here:

http://www.skritter.com/vocab/listsect?list=agVza3JpdHIWCxINVm9jYWJMaXN0SW5mbxit--oDDA&sect=0

James