I'm not sure why you're downvoted, the AOL search log case was a huge mistake on the part of AOL and I'm quite surprised that Yahoo! would take a risk like this. The real risk is never in just this data but in combining it with other public datasets. I haven't looked at what is in this particular dump in detail but if there is data that had to be anonymized (as they claim) then you can bet that there will be people already busy trying to reverse that.