The judge may have said it can be used in this one case, but unless struck down by another court, it sets up a precedent for other judges to do the same.
The precedent is already there. (Leaving aside issues of which precedent is binding v. persuasive v. nobody cares).
Service by publication--you just put ads in generally available newspapers--is allowed in some courts when you can't reach a person, a leftover from the days when people read newspapers.
A few years ago slashdot posted an article when a judge allowed service by *email*. The reasoning was that an email to the person was more likely to reach them than service by publication, which would have been allowed.
When service by publication would be permissible, most savvy judges are likely to allow service by email, if it is within their discretion to allow it.