Are there any risks/side effects to including cyanobacteria into my diet?

Treat it as an herb: A normal, healthy person should be able to eat Asian hair moss, a type of cyanobacteria (looks like a strange plant). It can be added to soups and stews, in moderate amounts, similar in amount to adding a half-cup of cilantro or bean sprouts. Variety is the key in nutrition. Problems occur when a person eats too much of just one plant, so a bit of hair moss once every week or two should be fine.

Yes: The source can be contaminated. Not worth the risk, as there are no good quality studies to say that it has any benefit. See this article: https://www.livescience.com/48853-spirulina-supplement-facts.html