A version of this has existed for years in the teachers’ room – ideas in books with good indexes and photocopiable pages get over-used while others are ignored. In the same way, things which are easy to find in books like Present Perfect Continuous and Prepositions of Position are over-taught while language points which are a pain to find stuff for like “collocations with ‘take'” get rushed through with just the stuff in the book or entirely ignored.
Search engines actually improve things for some kinds of language that might have been ignored, because it now takes seconds to find “idioms about money” and “words ending with -ship” for previously neglected language points like chunks and word formation – and often not that much longer to find EFL versions now Google recognises that people who include TEFL/ TESOL/ ESL etc in their searches are probably interested in all of those results. However, there are other kinds of language that are difficult or almost impossible to search for because they are such common words that they appear in virtually every page related to TEFL/ TESOL/ ESL etc.
For example, Googling “want to efl” and “teaching want to” gave no useful links on the first two pages of results. I did eventually find one useful result by Googling “how to teach the verb want”, but we can imagine that most teachers will not be so patient. Can’t think of any other examples at the moment, but I give up searching for stuff and have to start brainstorming and writing my own worksheets all the time – and again many teachers have neither the time nor the patience for that.
The other two issues are whether certain kinds of activities and sites that we might not encourage might often come top of searches, and whether sponsored links might make that even worse.