It should be obvious to anyone in the situation of having huge data storage someone might want to see for the sake of litigation to fight this kind of raid tooth and nail, all the way up the appeals ladder, and using every delaying tactic known to man and even to lawyers.
Why?
Because, as someone already noted, getting the data, and the eyeballs, and even the log-ons to the website is utterly dependent on the trust and good will these companies develop with their customers. If searching on Google or LL for, say, BDSM, or terrorist, hits, however innocently, might be unearthed and held against you by your employer or the FBI or fookin' ANYBODY is going to make you stay away from Google or LL. Giving up that kind of data is pure poison for any company like that.
As for the Viacom thing, Sumner Redstone, the ancient curmudgeon who controls Viacom, is on record saying that litigation, whether legitimate or not in itself, is a legitimate business strategy. And it is customary for lawyers to ask for the moon on behalf of their clients. So expect a lot more of this sort of thing cropping up, and not just from Sumner Redstone. LOTS of lawyers are going to be demanding the family jewels from lots of online companies.
It is up to the defendants to protect themselves, and they damn well better,or they will be replaced by companies who understand they MUST NOT release information their customers would not want to see sent to their spouse, employer, church pastor, local newspaper or worst enemy.
LL take note. I think about 95% of the people playing out personal fantasies on SL do NOT NOT NOT want their LL logs revealed to people with malicious intent toward them. LL, ignore this, and you ultimately will die.