I found this out on two of my new sites. For example, you have a new site and you want that it is ASAP listed in MSN. So you get few good backlinks and then you are waiting and checking from day to day if the site is in MSN index (not just crawled). Fastest was is this one: When your site will receive "a visitor" with referer http://search.live.com/result.aspx?q=www&mrt=en-us&FORM=LVSP your site should be in MSN index. Maybe someone already knows that, but for few this is new info. Have a nice day.
If your site is not indexed, definitely it will not show up in SERPs. So I don't think this is a new info, instead it's just common sense.
Yes, but this "visitor" isn't human... it from MSN spider probably, what mean that you are in index. Because for search term www, you probably won't get human visitors. It is a kind of sign for being indexed.