"Sweating" heater hoses???

[Zedder]

I was out in the garage the other day looking at what I needed for the L79 to get it ready of this season and noticed that my heater hoses were covered in an oily feeling liquid??? Having never seen this before, I posted on a Corvette site that I visit asking what was going on. Two other members noticed the same thing this weekend on their cars, but none of us know why this is happening. One of the guys has brand new hoses!!! So what's going on here? Anyone else notice this before? Inquiring minds want to know!