A 2008 Microsoft paper described eras largely in terms of the relationship between computers and people. In the mainframe era, one computer served many people. In the PC era (for analytical purposes, Microsoft apparently did not see the mini-computer era as qualitatively significant) there was one PC per person. In the 2000s, which Microsoft describes as the mobility era, there are several devices per user. In the coming ubiquity era there will be thousands of computing devices for every user.
You might therefore represent the change quantitatively. But it is the notion of pervasiveness that probably gets to the heart of the matter. In any era where computing is literally embedded widely into the fabric of life, “computing” itself fails to stand out. It becomes something like electricity, an underpinning more than a discrete pursuit.
Nobody would call the present era the “era of electricity,” as one might have spoken of the “age of the automobile.” 
In fact, geologic time is the polar opposite of computing or Internet time, where the taxonomy of eonothem (eons) , erathem (eras), system (period), series (epoch), and stage (age) are used to refer to the layers of rock that correspond to these periods of geologic time. On a scale where the most-granular measure of time is “millions” of years, the entire history of computing occurs on a time scale too short to measure.
To the extent that one can apply the geologic taxonomy, the Internet eon and pre-Internet eon might make sense, as use of the Internet spans multiple computing eras.
Perhaps we are have mistaken eras for ages or epochs, though. Mainframe, PC and mobile “eras” might be better seen, from a longer time frame as ages, epochs or periods within the broader framework of tool use.
The point is that people might instinctively sense that Internet, broadband, web and apps have some significance in the history of computing that we’ve not had time to digest and put into perspective. Clearly something important has happened with the Internet, and clearly something important is coming in terms of mobility and mobile devices. Precisely how that fits with the taxonomy of computing is not so clear.
