Fu Ling returns around 2,120,000 results in Google. The commonly used specie is (Bai) Fu Ling (white Poriae Cocos, Sclerotium) which is a compact mass of hardened fungal mycelium containing food reserves.
At least 30 formulas come to mind immediately that contain this herb and so it comes without a surprise that it takes position three of the most popular single ingredients (according to what has been prescribed by practitioners over the last 6 months).
As a superior class herb it can be given for a long time and there is a small risk of side effects – when it’s used for the right syndrome or situation.
“Fu Ling is sweet and neutral. It governs the treatment of rebellious qi in chest and ribs; [treats] worry, anger, fight and terror; [treats] congested pain under the heart; [treats] chills and fevers, vexing fullness, and cough rebellion; [it treats] scorched mouth and dry tongue; [it] promotes urination.” 
It appears in the category: Herbs that drain dampness and good quality is supposed to be hard, solid, white and sticking to the teeth on chewing.
We are little concerned that for a few months now, an Import Permit is required for all commercial consignments of Fu Ling and products containing Fu Ling. And not only does it require an import permit, but all such consignments (excluding some products containing Fu Ling extract only) require mandatory treatment with gamma irradiation at 25kGray prior to release from quarantine. This is to avoid the spread and incubation of potential harmful components. Blood products are also gamma irradiated.
We are just not sure what the effects of the irradiation process are and to what extend the product is affected, and hence are looking into it.
If you have any information on this topic, we would love to hear from you.
 Shen Nong Ben Cao Jing – from Dr Arnaud Versluys Note compilation of Canonical Training