Yahoo Answers choice for a good engineering database

I was testing Yahoo Answers and I asked the following question:

which is a good database to do engineering literature research?

And the answers were satisfactory for me: Compendex, CSA and Scopus

and I also get this valuable advice:

"better yet, ask your local librarian which databases that she/he would recommend for you to search. They usually know good places for starting research projects."

I strongly believe that there is a huge benefit for the scientists, researchers, engineers and students of implementing similar services within all these mentioned products. Indeed Engineering Village's Ask an Expert does something similar behind the wall.