I only have a very bijou collection but so far I have doubles of Posey, Blossom and Moonstone. But Posey and Moonstone probably don't really count because the second Posey (the good one, with uncut pink hair) is actually my daughter's and the two Moonstones belong to my daughter and son respectively.
Blossom stalks me a bit, she seems to be in every bundle I watch on eBay. She's my favourite and was my childhood pony so I would be happy to have an army (my husband not so much)