Why Anna?

I'm really wondering why Anna would take Sydney, and for that matter, how she even knew where Nicole and Sydney were.  There's something very fishy here.  Maybe it's revenge against Stefano for his treatment of Tony but what would her ultimate goal be?  Does she expect to keep Sydney? 

I don't think Kate has anything to do with it.  If she does, I'm definitely going to put my foot through my TV because she's just done way too much harm in Salem as it is.  Who else has an interest in kidnapping Sydney?