Q:

Do people pluralize "WiFi" with an "s"?

I'm in a friendly argument with a supervisor about this one, and I'd like some data: Does one say "WiFis" when referring to multiple WiFi networks, or does one say "WiFi"?
I suppose alternately, one could just say "WiFi networks," but this is more concerned with descriptive usage than prescriptive usage.

A:

I've never heard that in English though it is used in other languages. It would seem very strange since there is no such thing as a WiFi, so why would there be many WiFis?
WiFi is not used as a countable noun in English, you don't say I have a WiFi or anything similar. You instead refer to WiFi networks and that is often abbreviated to WiFi. However, since it is a contraction of WiFi networks, it is not used in plural form. So, to refer to many of them you will pluralize networks and keep WiFi as it is.
My position is also supported by NGrams:

While there do seem to be some hits, a quick look at those that could theoretically refer to WiFi (the ones that were written after WiFi was invented) shows no cases where WiFis was used to refer to WiFi networks. The older ones seem to mostly be errors in transcribing wife's.

A:

Do people do it? Certainly; even within StackExchange you can find examples like restricted WiFis or high-bandwidth WiFis. The Wi-Fi Alliance doesn't seem to provide any guidelines on the matter. 
But that said,

A search on COCA turns up 1001 results for Wi-Fi, 78 for WiFi, 4 for Wi-Fi's and 1 for WiFi's— all marking a genitive rather than a plural— and 0 for Wi-Fis or WiFis.
A search on GloWbE turns up 7 results for WiFis, all but one found in comments posted to blogs. 
A search on the BNC turns up zero results for any permutation.

The issue is not a question of pluralization, but that in English, Wi-Fi or WiFi is not in widespread use as a synonym for a WiFi network. This is certainly the case among writers and most technology professionals, who understand Wi-Fi as the marketing name of a particular technology protocol. Wi-Fis would be ambiguous, as it could refer not only to networks or SSIDs but, for example, to access points, or to multiple versions of the protocol.

A:

The accepted answer, asserting that WiFi is not a noun, is incorrect.  WiFi is clearly a noun.  It is probably used mostly as an uncountable noun.  We are unlikely to say "I have two WiFis," just as we wouldn't say "I have two furnitures."
However, as choster's answer suggests, some may be using it as a countable noun.  A google search for the exact phrase "there are two wifis available" yields one result with a snippet from a tripadvisor review saying

there are two wifis available, pick the right one -depending on where you are and you can surf no probs unlike some of the reviewers who experienced trouble.

It's probably good style, for formal writing, to avoid this, but the question asks "do people pluralize 'WiFi' with an 's'"; the answer is apparently "yes."  If the question were "should people..." then the answer might be "no."

