When Powerset was a media darling and getting lots of attention in the mainstream press, I set up a standing search for the keyword "Powerset" on Google news. Since I'm a bit of a news junkie, I regularly check the results. The original results were pretty good but as Powerset has fallen from the limelight, I've noticed a gradual decrease in quality owing to an expansion of "Powerset" as "power set". What's interesting is that the keyword results for "power set" typically are false positives where "set" is in fact a verb, as can be seen in the screenshot below.
This is an excellent example of where semantic search offers an improvement in precision over simple keywordese (which treats text as a bag or a list of words). A decent parser ought to be able to detect that "set" in these examples functions as a verb. Assuming that the query is analyzed as a noun (and that the analysis is respected in its expansion as "power set"), results where "set" is a verb should either fail match or at least be significantly lower ranked. A bag of words is nice, but a tree of words is even nicer.