What's really odd about this is that it doesn't happen to everyone and those whom it does happen to are sometimes very sketchy in the details or reluctant to send their boxes in so that they can be investigated (without cost - that can be arranged through a supervisor as I've done so through personally). I currently have two PS3 units (an original launch unit and one of the other non-backwards compatible newer units) and both updated fine with no issues. I'm not networking or downloading a lot of stuff from the PlayStation store (patches and DLC mainly). My guess is that if the HDD is getting corrupted by the patch, it could be a severe write issue or the HDD is closer to full. Since most of Sony's patching is downloaded and then decompressed before installation, that could also be a reason why this happens.
In the view of this lawsuit, I'm not sure if it will go very far. Sony may just opt to exchange or replace all of the named plaintiffs on the suit with brand new units and make some mild change to their warranty policy (much like Microsoft did in the light of the RROD issues). If they are truly shrewd about this, they will then take the units they recover and check to see what all the affected units have in common with regards to updates, games played, downloaded DLC, etc. Since this is such a limited affect, my guess is that there would be a combination of obscure things that would draw this out but the more units they recover, the easier it would be to isolate.
As for firmware updates and upgrades, with all the new consoles, it is part and parcel of how things work. To that end, Sony, Microsoft, and Nintendo all have a responsiblity to ensure that their hardware is functional at all times and should be much more amenable to exchanging or servicing hardware if they can physically determine that something based an update they've passed is the cause. That, I think, is the primary issue at root for a lot of people's arguments (and also that Sony has the audacity to introduce a new product to market which is non-inclusive).
I've never had the experience of hardware failing with Sony (I have with Microsoft and it was a pain to go through) and so I can't speak directly with any experiences with them. I did break the analog stick on my first PSP but even then, I had not issues with getting it repaired by them (and yes, I paid the fee).