In Livermore, this awareness is having some consequences. The owner of Westover Vineyards (in Palomares Canyon, just west of Livermore) announced that "we have decided to retire," after about 30 years of winemaking.
There's more in this article from the LIvermore Independent:
Wendell Lee, General Counsel for the Wine Institute, suggested that wineries using volunteers consult with an attorney familiar with labor laws. He noted that the use of volunteers by a for-profit business can lead to labor code violations. The penalties can be very severe. Minimum wage, payroll taxes and workman's comp are all triggered. The volunteers cannot be paid with wine.
I am not a lawyer, but it seems like a big deal to me. Interns are still allowed, but those come with their own set of restrictions. Unpaid internships have to primarily benefit the student, and have a significant educational purpose. I can see that happening with winemaking students, who come to learn as much as help out with harvest, crush, cellar work, etc., but it's hard to argue that the folks operating a tasting room and getting paid in wine are being educated in the same way. I also don't know what the law is in other states.