Yes Cyano -very interesting. It actually says not to worry if you get just a few sprinkles. But if you get mats remove the mats because once the mats develop they shut down the metabolic processes below and in essence feed themselves because biological filtration is diminished due to the mats.
I guess that would also answer the question some people have about:
"I can't siphon it off should I blast it off the rocks or would it just cause it to spread?"
Answer is blast it if you can't siphon it (just lifting the mat off somehow and tossing it would be best) because if you let the mats grow you are pretty much feeding it.
Much like bryopsis once established the cyano sustains itself in that way and won't need much input from the water