There are a few things that this could mean though. One being that it was a implemented ages ago and is a glitch that was never removed or thought about. Another idea is floating around that Google could be preparing for a free service along side a paid unlimited service. The support page didn’t offer up any answers to the issue nor could we find any information mentioning any sort of cap other than the 20,000 song upload limit. Which has nothing to do with a streaming limit.
I have streamed countless hours of music through my Google Music account to my TV via a Logitech Revue, along with hours through my device while cleaning the house. I have yet to ever receive a message or have my service stop streaming. It seems as though the reported cases of this happening are pretty low. If Google is indeed starting to cap the number of songs or setting a data cap on your stream they need to make it known to people.
Droid-Life hit them up for an answer and I may just go ahead and place a call in and see what the story is.
Source: Droid-Life