One strength of Wikipedia, and a central factor for its growth, is that it does not restrict contributors. On the other hand, this leads to many inconsistencies within Wikipedia, especially between the 251 different language versions.
The Web is currently changing from a medium to publish and share text documents into a medium to publish and share data.
DBpedia is one of the largest multi-domain ontologies that currently exist.
Terms from DBpedia can be used to annotate Web content. Compared to other subject hierarchies, like the classic ones used within libraries, DBpedia has the advantage that each subject is backed by a rich description including abstracts in 14 languages.
DBpedia contains information about geographic locations and is interlinked with other geo-related data sources such as Geonames, the US Census, EuroStat, and the CIA world fact book.
One nice thing about Wikipedia is that is kept up-to-date by a large community.
Wikipedia currently only supports keyword-based search and does not allow more expressive queries like "Give me all cities in New Jersey with more than 10,000 inhabitants" or "Give me all Italian musicians from the 18th century." This lowers the overall utility of Wikipedia.