[tensafefrogs]

You can still track users just fine without Flash - the VPAID spec calls for allowing cross-domain "Friendly" scripting access, which is horrible for users.[1]

The only problem with Javascript adoption was the availability of Javascript based ads and support for this VPAID style tracking.

[1] http://www.iab.com/wp-content/uploads/2015/06/VPAID_2_0_Fina... - VPAID 2.0 spec, section 8.1.3: "The VPAID ad unit is rendered within a friendly IFRAME (FIF) and can access the DOM of the page in which the player is rendered."