"AND" operator is unnecessary-we include all search terms by default

Really? Why are the search results totally different then?

[sandpetra]

Really? Why are the search results totally different then?

[jenniann111]

I have no answer, but you're right, they are different. Why I wonder?

[g1smd]

Try searching for something that includes a hyphenated-word and then search again with the hyphen replaced by a space.

Hmmm. Where did all those supplemental results then come from?

[selomelo]

As far as I can see, the only search engine that really ignores stop words such as "and, the, a," etc. is the MSN. Try a simple search "city and fire" and another one without "and," that is to say, "city fire." You will see that both results are identical.

When you do the same experiment with Google, you get totally different results. For example, New York Fire Department comes as #2 when you use "city fire." But it drops down to #8 when you use "city and fire."
A more drastic example would be the #3 in the "city fire" query. Sacramento Fire Department comes as #3 with this query. But when you repeat the search with "city and fire," it drops to #33, in other words, page 4!
Therefore, a simple "and" or any other stopword in that matter may mean life and death in terms of visibility.

I guess that this difference comes from so called "keyword proximity." When calculating proximity, Google (and Yahoo) seem failing to ignore stopwords.