A380.
 

A very large aircraft. Should we worry about wing cracks?

Yes!

Any aircraft that has a crack ANYWHERE, needs checking. Why do you ask? Hopefully, not a doubtful YouTube video.

Considering the current "no hull loss" and "no cracked wing" status of the A380, I think Airbus and the authorities have a point when they say that those cracks are not serious. :8

Although it is not really potentially serious in the short-term, it might have a devastating effect in the long-term. Sometimes I feel like the QF31 incident occurred to make us aware of such wing cracks before it gets too serious and leads to a hull-loss.
The Aviation Herald report makes it clear what the Airworthiness Directive thinks about it, I think you should read that.

The term "Wing Cracks" is incorrect, as it implies a far more dangerous condition than it really is. It evokes a picture of cracks all over the wing, with bits falling off.

See Tech Log for some facts.

The Times today described the cracks as being in the roots of certain brackets where they are attached to the wing structure, internally, and while unrectified these cracks could eventually affect the wing integrity, they do not at the moment.

And that seems to me to be about right, judging from what the experts in Tech Log say, although you need to sort them from the BS merchants. But I am not an expert in composite structures.

Problem is, so few of us are, including most of the LAME community.

I have to agree with Capot.

Ok we have a wing that initially failed it's loading test, now we have statements that these fixtures are composite and were installed for production purposes being less than secondary structure... Sounds like Airbus installed these fixtures as a light weight resolution to pass the wing load test and they are now the weak link. They have been found as a result of fuel leaks and catastrophic engine failure driving someone to inspect the wing. Aluminum is a bit heavier but it bends before it breaks as is the opposite with composite structure. Now we have a CAA mandate to inspect this aircraft.

The problem now is what do you do to prevent these fixtures from breaking W/O adding weight to the aircraft and maintain the wing loading expectations of the CAA.

Granted much of what I have said is based upon 2nd hand information and speculation based on my readings of the progression of this aircraft from design to operation. The wings are not likely to fall off... YET. Here is an interesting link to insight on the massive wing flex this aircraft endures (composite material does not flex well).