While it is odd that so many large tech companies haven't highlighted their presence in Africa, there are some notable omissions from that list. Microsoft, for example, have clearly listed contact points and targeted support pages all over Africa, including Kenya[1], and SAP has a number of operations across Africa[2].
The reason for Google not listing their Kenya office seems to be to do with the type of office it is[3]. They do have quite a few jobs listed in both Kenya, and the author's own city: Kampala in Uganda[4].
Perhaps when the tech industry matures, we'll see the kind of coverage a large manufacturing company has[5].
[1] http://www.microsoft.com/worldwide/phone/contact.aspx?countr... [2] http://www.sap.com/contactsap/countries/index.epx [3] http://whiteafrican.com/2008/07/04/google-kenya-and-the-goog... [4] http://www.google.com/jobs/africa/ [5] http://toyota-africa.com/cars/new_cars/index.asp