SSD's do fragment, but because they are a different technology than HDD's, the data being scattered over a wider physical area doesn't affect performance in any way.
From my understanding of how SSD's work, SSD's attempt to be as random as possible when writing data, so I imagine that when its working correctly it is in fact if quite fragmented.
Though the first post is true, dont defragment SSD's. Gives no performance boost and uses up its read/write cycles very quickly.