I would personally point to a framework like Meteor as my example. Having a framework handle all of the reactive parts of your code with no additional work, and giving the end user a way to simulate database updates on the client side while it's being processed server side is a huge win for performance.

Now of course none of this was impossible to do before, but the advent of all major browsers now supporting web sockets, and the existence of this framework and community which has already solved all of the hard parts of the implementation makes it actually feasible.

Software defined radio[1]

[1] http://en.wikipedia.org/wiki/Software-defined_radio

Bad example; SDR existed in prototype form as early as the 80s, and the USRP has been commercially available since 2005.

Yes, but today you can order a USB SDR radio for under $10 and you have a crapton of FOSS software to use with it.

I was thinking of things like deploying auto-scaling SOLR clusters for hundreds of dollars, vs tens of thousands for dedicated search infrastructure years ago - maybe a bit more than 5 years, but that's the gist.

Twilio. Maybe Twilio is within the 5 year window too.

Mobile apps in general - the hardware infrastructure in peoples' pockets lets us do stuff with software that was not on most peoples' radars 5 years ago.