Not a deluge yet
On our rather esoteric web site (www.nber.org) that browser string accounts for 5% of the last week's 5.04 million hits. So it isn't killing us yet, but then what fraction of their users have upgraded so far? It certainly seems tempting to serve up an error page to the user, asking that they disable the "feature", should they eventually select one of our pages.
Why should they be scanning pages before the user clicks? Perhaps they don't have the proper hooks into the browser? Or don't know how to use them?
Daniel Feenberg