No sympathy whatsoever.
If your business is SO dependent on mobile networking, then, in the same way you always make a safe, reliable set of daily backups for your important data, you should already have a contingency plan for such events. Such as a cheap PAYG secondary driver.
Blaming o2 for your 'loss of business' is like saying 'I always meant to get those backups done...'. And people are asking for compensation? Seriously?
And the way the Sky news anchor was absolutely ripping into the CEO of o2 last night was ridiculous - literally asking if he was going to resign, and virtually demanding financial compensation...
I would imagine there is plenty of contract clauses that cover unforseen issues such as these. I think the country as a whole needs to stop jumping on things like this - we're ALWAYS so quick to blame everyone else for our own oversights.
(I'm not suggesting that there are not SOME legitimate complaints about what happened - but these will be special cases, and I imagine o2 will already be dealing with such companies due to contractual obligations)