If 15-20% of top companies are using twitter for customer service, that is a tremendously good thing.

To frame it another way, if you told a startup that 15% of top companies would be using their startup for customer service within a few years of launching, most people would take that in a heartbeat.

Also, this early I don't think the actual number is as important as how fast its growing/shrinking. It'd be useful if they showed us last year's number and I'll be curious to see next's...