This particular example looks like it was piped, but I think I would try extruded fondant strands. (Unless you have a steadier hand than this decorator had!)
I noticed that....the fondant squares, though, are perfect and flawless!!!!
Nyxandra, another idea is to comb lines of SugarVeil Icing with the Confectionery Comb, and when they are set, peel and place them onto your cake. Here's the process: http://www.sugarveil.com/confectionery_icing/comb_techniques.htm and here's an example of what the strings look like: http://www.sugarveil.com/gallery/small_cakes.htm (the pink dotted cake on the left middle of page). Since the lines are combed, they are absolutely perfect, and easily done.
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