Some search systems don’t handle punctuation well. This can lead to incorrect search results and confusion.
For example, my public library’s online catalog finds nothing when I search for “ooh la la! it’s beauty day” but comes up with results if the exclamation mark is removed. On the other hand, the Barnes & Noble and Amazon sites handle the punctuation correctly.
A recent usability participant said that he uses Google to search everything, including individual Web sites. You can do this with the “site” keyword in Google, which restricts the search to the site you indicate. For example, search for “site:amazon.com beauty day” and you get only results matching that string at Amazon. He uses this so he doesn’t have to figure out how each site’s search system works.
If the search system on your site or app is different from what most others do, your users will be confused. They’re not likely to spend time figuring out why yours is different, they’ll just get frustrated and leave. Look at log files to see what people are entering as search terms and be sure your system can handle them.
For better or worse, it’s a good idea to copy what the most popular search engines do because that’s what people are used to.
More: Details about keywords and operators in Google searches