ABC will enable live-streaming of its programs through its iOS app, moving beyond an on-demand only programming model for the first time. The "Watch ABC" live feature will no doubt please a subset of the people who have downloaded the ABC app 10 million times to date and who still value live viewing. But Watch ABC will also likely puzzle and irk some users when they discover they must be authenticated as a pay-TV subscriber in order to access the live stream.

In fact, requiring authentication for Watch ABC is just the latest evidence of TV Everywhere's tightening grip on broadcast TV. Another recent example was NBC making large portions of last summer's Olympics available only to authenticated pay-TV subscribers. In addition, Fox has maintained an 8-day exclusive window for pay-TV subscribers for almost 2 years.

Not surprisingly, these broadcast TV networks are all part of larger media companies with significant cable networks. Cable networks - and pay-TV operators - are increasingly invested is seeing TV Everywhere succeed because it adds value to the expensive pay-TV subscription and blunts the appeal of over-the-top alternatives. To extend TV Everywhere's power and enhance their negotiating position for retransmission consent fees, broadcasters are carefully limiting what will remain freely available online and what will be placed behind the authentication paywall.

TV Everywhere's pull is so strong that I'd bet that as other broadcast networks also introduce live streaming - and other new features - virtually all of it will require authentication. It wouldn't surprise me if even the days of being able to access the most recent 5 episodes online may be numbered.

But as broadcasters are pulled into TV Everywhere, competition from newcomers like Aereo could become more appealing. For $8/month Aereo offers all of the same live streaming access Watch ABC does, but it also gives access to other networks' programming, along with DVR capability (and improved pricing as of today). For those who value live viewing of broadcast TV on multiple devices and are price-sensitive, Aereo provides an alternative to expensive pay-TV bundles.

Whether Aereo has a compelling enough value proposition remains to be seen. But Watch ABC is further evidence that alternatives like Aereo are helping prompt continued innovation by broadcasters. Increasingly though, this innovation is not just meant to please viewers, but also to support larger corporate priorities.

Note: At the VideoNuze Online Video Advertising Summit on Tues, June 4th in NYC I'll be interviewing NBCU's EVP Lori Conkling. Among other things, we will discuss the role of live streaming, authentication and retransmission consent. Early bird discounted registration is available until this Friday.