My attempt at pumping Pleiades through yahoo pipes led to an interesting discussion with Tom Elliott, the direct of the Pleiades project. Tom writes
As Shawn observed, pumping that list of ancient names through a presentist geocoder (like Yahoo!’s) gives you suboptimal results.
Pleiades in fact stores locations for every feature (at least when we can determine their locations). In our customization work on Plone for Pleiades, we’ve tacked on a couple of other interfaces that aren’t as obvious to users as they should be. Anywhere Pleiades displays or lists spatial content, we also provide an Atom feed that’s extended with GeoRSS tags, as well as a KML feed.
So, for those archaic places, Shawn could choose to use either of:
Both provide the coordinates, and therefore get you around the geocoding problem.
The full text of Tom’s post is here. Thanks Tom! I’m going to see what I can do with those new feeds…
Electric Archaeology 
Using Tom’s suggestions, I’ve added distinct feeds for each period of Pleiades place data. It works – but I’m intensely frustrated with Pipes today, since every time I add a feed or otherwise alter the pipe, the whole site crashes on me. What good is that? C’mon Yahoo…
Anyway, Pleiades Project Pipe lives here .