[dclowd9901]

StackOverflow also provides job-finding/head-hunting services, and yes, they could probably successfully argue that they have ownership of "the Stack name" with regards to the space of job placement, given they've exercised that name into many variants of Stack*.

[travem]

StackLead isn't providing job-finding/head-huntiong services though, from my reading of their site they are more suited to sales lead management.

A quick search of USPTO shows plenty of other companies using stack in their registered trademarks. The search results don't appear to be linkable but starting here -> http://tmsearch.uspto.gov/ it shouldn't be too hard to find plenty.