UPDATE: Heathrow is saying that Samsung didn't officially buy "naming rights" to the terminal. Take that at face value - because it seems like Samsung thinks they did!
In an effort to cause as much confusion as possible at the self-proclaimed "world's busiest terminal," Samsung has purchased temporary naming rights to rebrand the terminal as "Terminal Samsung Galaxy S5."
This is most definitely a digital marketing first in travel, as there's no other documented case of a brand - tech or otherwise - purchasing all available signage in an airport setting. And it has serious potential for blowback, as weary travelers may push back from the overwhelming brand permanence during an often-stressful transit experience for the 1 million+ passengers that will pass through in the 2 week period.
This means that travelers will not be able to escape Samsung - the messaging goes on all the digital panels in the main terminal, gate rooms and baggage reclaim area, and signs in the passenger lounges will point travelers to try the new S5 in terminal's Dixons Travel stores.
Russell Taylor, vice president of corporate marketing at Samsung Electronics UK & Ireland:

We are always looking for ways to maximise brand impact and this activity is testament to that. The partnership with Heathrow Airport and JCDecaux Airport was a one-off opportunity to push the boundaries like no other brand has been allowed to do before.
The campaign was conceived by the agency that Samsung owns, Cheil UK, in a concerted effort to reverse the downward trend of market share in the UK - Samsung went from 36.7% to 30.2% in the first quarter of this year.
Of course, the airport is not just catering to UK residents and offers a significant international platform to market the new phone - a very efficient marketing platform, to be sure. Not to mention the many media impressions Samsung has received simply by announcing the takeover.
Samsung spent $13 billion on marketing in 2013, and no word yet on the cost of the terminal naming rights.
It's unclear whether the naming rights also extend to communications between pilots and the control tower, resulting in exponential delays as hundreds of pilots trip over the much-bloated temporary terminal title (that's a bit tongue in cheek, but then again, it's all a bit ridiculous, isn't it?). Only time will tell if the future of airport/tech marketing is bold moves such as this, or if the campaign fizzles.