You quite possibly have already used one, and if you haven't, you are likely to do so soon.
Rateless erasure codes (fountain codes, raptor, whatever name you use) are nothing but "secret sharing" if you want to look at them from the right angle. Indeed, the Reed-Solomon coding on a music CD is secret sharing... so if you've ever listened to a music CD, there you go.
They are used in present-time and future media sharing applications.
One fundamental problem with distributing huge amounts of data to large number of clients is that a server can only do one thing at a time. Thus, you can only either process data live as it comes in, i.e. it's being streamed, or you have to wait until you have received every piece to form a complete file. Which may, in some cases, take a very long time for the last segment to be received.
Imagine a checksum error in a segment somewhere in the middle of a terabyte-sized file. This horror even has its proper name.
Secret sharing in the form of a fountain code has the advantage that you only need any N pieces. So, no matter what, after a very finite time you are good to go. One segment was corrupt? Who cares, just use the next one that comes in.
Mainstream P2P sharing software like e.g. BitTorrent does not currently use secret sharing (simply because peers are cheap, the possible gains are limited...), but there exist implementations that indeed do so. It will remain to be seen whether such a thing becomes mainstream in the future.