responsive design - Is breaking established web conventions in order to be consistent across multiple devices an unexpected (and therefore harmful) user experience?

As a good working example: The standard convention is for mega menus to appear on hover (see sites such as play.com and next.co.uk).

This fits with Jakob's Law of the Web User Experience which states that:

"Users spend most of their time on other websites." which means that users prefer your site to work the same way as all the other sites they already know.

However there are other websites that break this convention, such as Starbucks.com which opens the menu on Click instead of Hover. Presumably this is because they are going with a responsive website and have opted to provide the same user experience to visitors on a desktop machine to those with tablets.

Should you break established conventions and user-expectations in order for your site to be consistent across devices?

To quote Jakob Nielsen:

The more users' expectations prove right, the more they will feel in control of the system and the more they will like it. And the more the system breaks users' expectations, the more they will feel insecure.

^{Note: this question isn't about whether hover is or isn't better than click because we have several useful questions on this already. I'm more concerned with the idea of breaking convention for internal website consistency across devices.}

Answer

I believe that on occasions it is all too easy (lazy even) to follow the convention of others and thereby produce an experience which, by it's very nature of being similar to others, is neither unique nor remarkable.

Technology changes, and with changing technology, people's behaviour changes too. Without this we would all have identical experiences across websites.

I think we should break convention every now and then, particularly if there's a good business decision behind it, and of course, if user feedback and well executed testing shows it not to be a bad decision.

I think aiming for some sort of consistent experience across devices is an ok reason to break convention.

I congratulate those who defy convention and innovate to still provide a great user experience.

It is those who break conventions for no good reason; that do not align with the business goals; that do not seek the user research and feedback; that do not design on data driven evidence; and that create a confusing experience as a result, that do the damage.