In American English in particular it would seem that adverbs are slowly dying out in everyday speech, being replaced by adjectives. This is especially true for advertising language where it would appear that anything goes as long as it sells! As far as current grammar rules go, the -ly endings SHOULD be used in the slogan "Think globally, act locally". But can we say the other statement is WRONG? Reference books (dictionaries, grammar books) reflect the USE of English. If enough people use words in a certain way -- even contrary to the current grammar rules -- the chances are that the new forms will be picked up in a later version of the reference books and become the new standard.
Many Germans are concerned that English is infiltrating their German language (Denglish). In fact, a similar thing has been happening to the English language. Because so many non-native users are using English imperfectly and yet accomplishing their communication goals adequately, new forms of the language are being spread all over the world. On top of this, those who speak English as their native tongue are also spreading non-standard written forms over the new media at enormous speed whether it is due to the lack of proper education or sloppiness or just plain pragmatism that puts higher priority on speed rather than accuracy in our fast-paced globalized world.