Media 6 Degrees (the new owner of my former employer, EveryScreen Media), has changed it's name to "Dstillery".
This Fast Company article does a remarkably good job of explaining what the technology delivers. (Disclosure: I implemented the early mobile-phone IP-tracking algorithms when I worked at EveryScreen Media).
Whilst I do believe (from what I saw) that ESM/M6D/Dstillery take privacy very seriously; and will (continue to) behave in a responsible manner, I still feel a sense of unease when I think about the extent to which participants in the advertising industry are able to peer into people's personal lives.
To balance this (sort-of) criticism, I feel I should emphasise the fact that the advertising industry is, in general, a pile 'em high sell 'em cheap kind of affair, where advertising impressions are bought and sold by the million; where performance is measured in statistical terms; and where the idea of paying close attention to any one individual would be laughed off as a ludicrous waste of time.
However, it is possible that not all participants will feel that way, just as it is possible that not all participants will be as motivated to act responsibly as my former employers were.
There has been a lot of debate recently about NSA spying on what we read on-line and using our mobile phones to track where we go in the world. Well, you don't need anything like the NSA's multi-billion dollar budgets and mastery of (de)cryptography to do something that feels (like it could be) similarly invasive. (The advertising industry is an order of magnitude less creepy, but it is facilitated by the same social & technological developments, and is still heading in a very similar direction).
I think that this is something that we should think very carefully about, and just as we seek to find better ways to regulate our security services, so too we should (carefully; deliberately; deliberatively) seek to find ways to regulate the flow of personal information around our advertising ecosystem.
Edit: One thing that does bear mentioning -- the link up between M6D & ESM really is a smart move. From a data point of view, it is a marriage made in heaven (a bit of a no-brainer, actually); and I think that the insights that result from combining their respective data-streams will yield genuine benefits for their clients & the brands that they represent.