See for yourself.
- First, try a search for "valves".
- Next do a search for "valves -pumps". The first result is for www.breastfeeding.com, which does not have any on-page mentions of the word valve. Furthermore, it contains the word "pumps" very prominently in relation to breast feeding "pumps & pumping."
- Finally, just to see the extent of the brokenness, do a search for "valves -12345678910111213". Hopefully, I have picked a string unlikely to occur in any common search result. However, instead of returning the original set of results, we are back to breast pumps and motor sports.
In light of Yahoo's "Social Search" initiative, I hope I'm not the only one who sees the irony in this.
In the process of showing this to co-workers, we stumbled upon another interesting "feature", this time in MSN. MSN ads do not handle the minus operator. Try a search for "valves -pumps".
The "contextual" ad results are exactly what we subtracted from the query, with some stemming! Try just "valves" to see the difference. Thanks to my co-worker, Joan, for pointing this one out to me. Possibly a result of the way their ad code is parsing the query terms?
That's about does it for today's search engine "feature" round-up.