Microsoft, after having for a long time used common words as trademarks (Windows, Internet Explorer, Word, etc.), is trying to reuse AppStore name for its own store, and states that it sounds generic.
From macnn’s article we find interesting points, and this conclusion :
Disputes over generic usage have been a staple of trademark in the past few decades as certain products, such as Coke, Kleenex, and Xerox, have been commonly associated with the type of product rather than a particular brand. Apple can’t prevent common, non-commercial use but can try to prevent other companies from making similar references.
We also remind an old Painter like application on System 6/7 (mac), that was named Expression, and whose version 3 (available on MacOSX and Windows) seems free since the company (Creature House) was bought by Microsoft in 2004. Development of the application has then been halted, and Microsoft reused the name for its design toos suite for Silverlight based applications’s client side (user interface).