In think any situation where, from an acquiring company's perspective, the decision becomes one of "build versus buy" fits the description of a pure technology play.
SO there's GOOG/YHOO/MSFT/AMZN/etc, but there's also places like IBM/EMC/HP/CISCO that are going around spending lots of cash.
So look at edge cases around Enterprise Solutions where new tech (or moore's law) lets us do things that were too expensive previously. Some previous examples:
Data Deduplication: Data Domain --> EMC, Diligent --> IBM
Config Management/Provisioning: opsware --> HP, Rembo --> IBM
