Timo Arnall from the design studio BERG has makes several great and provocative points in his essay "No to NoUI" -- a well-argued piece that opposes the idea of "interfaces that disappear" and "seamless computer interfaces," arguing that by hiding the working of computers from their users, designers make it harder for those users to figure out what the computers are really doing and to solve the problems that inevitably arise.
Interfaces are the dominant cultural form of our time. So much of contemporary culture takes place through interfaces and inside UI. Interfaces are part of cultural expression and participation, skeuomorphism is evidence that interfaces are more than chrome around content, and more than tools to solve problems. To declare interfaces ‘invisible’ is to deny them a cultural form or medium. Could we say ‘the best TV is no TV’, the ‘best typography is no typography’ or ‘the best buildings are no architecture’?
...We might be better off instead taking our language from typography, and for instance talk about legibility and readability without denying that typography can call attention to itself in beautiful and spectacular ways. Our goal should be to ‘place as much control as possible in the hands of the end-user by making interfaces evident’.
Of course the interfaces we design may become normalised in use, effectively invisible over time, but that will only happen if we design them to be legible, readable, understandable and to foreground culture over technology. To build trust and confidence in an interface in the first place, enough that it can comfortably recede into the background.