The Formula for Good Design?

One of the most frustrating questions to be asked is 'Is this a good design?'. It is a simple question that encapsulates so much and is so subjective...

There are many qualities by which we can measure a design; does it fulfil it's purpose, does it look great, is it desirable, how will it last and so on. But these are more questions and are again subjective.

Good design is generally a combination of these properties. Yet there is one constant - good design must do something useful. whether it is useful in that it saves lives or it gives an impression of wealth makes no difference. A new, innovative product which does something not previously possible is always bonus though.

Here is one anecdote that made me think of my role as a designer.
 

3M designed a new glue which could stick paper to a flat surface, but it was not strong enough to do this for any length of time. This makes it seem like a defunct product... yet one of the company's scientists was in church and  realized that the glue could have stopped his bookmark slipping from his hymn book. Thus we have the advent of the Post-it note - a product most of us use daily!

So who really is the mastermind of the post-it? The team who created the glue, or the one who found a useful application. In my opinion, both of them and again this raises the question of influence vs. intention... 

There was no intention to create the Post-it note in that form and without that one man's influences would it even exist?

Of course we are led to believe most design is well intentioned and a process has been followed in order to create the best product available...

Maybe influence creates ground-breaking ideas and intention creates the best possible iteration of the time?