Their main products are oriented towards integrating structured and unstructured data from lots of different data sources: http://en.wikipedia.org/wiki/Palantir_Technologies#Palantir_...

Other articles on the company make it more clear that the reason why they need so many "forward-deployed engineers" are because they heavily customize the installed software for each customer, i.e. you have to do a lot of custom work pulling data out of Proprietary Customer Database X to feed it into the system (and back out). See "Why Palantir Makes My Head Hurt" http://kellblog.com/2011/06/27/why-palantir-makes-my-head-hu...