Technically, the data is not stored in the network, but in the buffer memory of the routers (and switches) in the path of the packets. So what this is really doing is externalizing the cost of storage to the network providers.
There is a problem called “Buffer bloat”¹ which is that many manufacturers of networking equipment provide too much buffer memory, which leads to TCP latency and timeouts, since TCP was not designed with these large buffers in mind. Using Pingfs will take up buffer space in networking equipment. This could either be a good thing, since it decreases the available buffer space, or it might be a bad thing since it might make networking providers increase their buffers.
I’m not sure how much of this comment is serious.
① http://www.bufferbloat.net/