Recent criticism of the use of myriad as a noun, both in the plural form myriads and in the phrase a myriad of, seems to reflect a mistaken belief that the word was originally and is still properly only an adjective. As the entries here show, however, the noun is in fact the older form, dating to the 16th century. The noun myriad has appeared in the works of such writers as Milton (plural myriads) and Thoreau (a myriad of), and it continues to occur frequently in reputable English. There is no reason to avoid it.
Examples of MYRIAD
There are a myriad of possibilities.
<the car can be outfitted with a myriad of options>
Mr. McCullough hails Adams for being uncannily prescient … foreseeing a myriad of developments, from the difficulty of defeating the British … to the divisive consequences of slavery. —Michiko Kakutani, New York Times, 22 May 2001
Sectarian Protestantism reinforced both American individualism and the tendency of the society to be self-organizing in a myriad of voluntary associations and communities. —Francis Fukuyama, Atlantic, May 1999
Out in the barrios, under the nipa palms, he listened to the myriads of humming cicadas and the call of the geckos. —Nina FitzPatrick, Fables of the Irish Intelligentsia, 1991
To read Marie Corelli, you had to be able to follow several hundred printed words at a time, and there were myriads in England who were up to it. —Hugh Kenner, A Sinking Island, 1987
… laced his fingers behind his head and stared at the myriads of tiny colored dots that make up darkness. —John Steinbeck, East of Eden, 1952
… the more quotations that could be found, the more easily the subtle differences between the (possibly) myriad usages and meanings of any single word could be identified. This is how historical dictionaries are made … —Simon Winchester, The Meaning of Everything, 2003
The age of white guilt, with its myriad corruptions and its almost racist blindness to minority individuality, may someday go down like the age of racism went down … —Shelby Steele, Harper's, November 2002
World War II accelerated the progress of science and technology into the microcosm. Scientists and technologists played tag with one another in their search for microscopic control. With mathematics and myriad theories, they defined a new microcosm. —Joseph A. Amato, Dust, 2000