Here's a tiny twist on WordCount that many, many companies use MR for (often their first foot in the water): you have many gigabytes or terabytes of web access

Here's a tiny twist on WordCount that many, many companies use MR for (often their first foot in the water): you have many gigabytes or terabytes of web access logs and need to bill customers via some API scheme like /api/3001?x=1&y=2 where "3001" there is the customer ID. You add some regex and now you're doing "WordCount" on the customer ID (per day, month, etc).