Add note about when.map being opportunistic
Add note about when.map being opportunistic

anthonyvia/when,SourcePointUSA/when,frank-weindel/when,mlennon3/when,caporta/when,ning-github/when,stevage/when,tkirda/when,anthonyvia/when,SourcePointUSA/when,mlennon3/when,stevage/when,frank-weindel/when,tkirda/when,ning-github/when,caporta/when