I was in Venice last summer and picked up a few pretty pieces of Murano glass and jewelry. Usually the jewelry is marked with a sticker or tag to guarantee authenticity.
Unfortunately all of this Murano glass jewelry CAN be replicated in glass and has been coming from China for many years at lower budget prices.
People like to buy the Chinese glass beads for pennies and make their own necklaces. It is very popular at the jewelry shows.
The necklace you like on Etsy actually states at the bottom of the description that the necklace was made in California but it does not say where the beads are from. It also does not use the word Murano at all in the description.
My thought is, given the low price, if you like it, buy it, as it is very pretty and colorful and is definitely glass, although probably not from Italy.