Presumably, they have some preexisting database that maps email addresses to personal information. Their Privacy page, however, is not transparent <i>how</i> exactly they got this data:<p>&gt; Broadly speaking, we collect information in three ways: (1) when you provide it directly to us, (2) when we obtain information about you or your company through trusted third parties or indexing systems, and (3) passively through technology such as “cookies”.<p>This is a disconcerting use of &quot;secret sauce,&quot; particularly since email addresses have the same weight nowadays as usernames.