Guess I'd better let you know about mine then.
Don't worry, it's not that bad, but you might want to check yours over when I tell you what I found.
Lift the bonnet and take a look down the gap where the top of the wing bolts to the chassis. About halfway between the bolts there should be a plastic shrouded cable dissappearing down the gap in question (this is the side indicator feed). If the gap is clear and (using a torch) you can see a fair way down, you have nothing to fear.
However, if you can see a lump of rubber jammed in the gap, it may be worthwhile investigating further. I assume it is wedged in there as some kind of anti-drumming/vibration measure, maybe to stop the cable rattling.
Unfortunately, a lot of run off from the windscreen is channeled through this gap and subsequently this rubber wedge traps dirt and moisture against the metalwork of the inner wing resulting in the inevitable.
My car has been on the road since late 2000 and covered about 64K, and I uncovered a large patch of rust, beginning to pit quite badly. Maybe in a year or two it may have perforated, although this area being structural to an extent will be quite thick. I was lucky enough to catch it and was able to repair and re-paint easily.
Needless to say, I didn't bother putting the wedge back in.
And the other side? It was never put in at the factory! The irony: slack workmanship by Alfa employee eliminates rust trap.
Unfortunately, if you do need to get at it, to remove the wing you first need to remove the plastic sill covers, which is a major pain in the arse. I havn't tried it, but there may be some scope for just taking out the top two bolts and easing the wing away whilst still attatched at the bottom, but make sure you don't lose the shims behind the bolts which are used to get the correct panel gaps.
It's a particularly nasty fault as it will generally remain hidden until it's too late. Hopefully mine's a one off, but how likely is that? Oh well, fingers crossed guys.