Hadoop is buzzword compliant, but every use of it that I've met was unjustified - it made things 10 times slower, more complicated and fragile compared to a straightforward mmap implementation. I guess it might start paying back if you can effectively use 100 machines and have them at your disposal - but I have not yet seen evidence of that.
The flip side of this survey: 46% have either deployed Hadoop or plan to deploy. That's a pretty healthy number and qualifies as "mainstream" adoption, IMO.