Today any court can require anyone to testify about anything, if that testimony is seen as relevant to a case, unless that person has a legal “privilege”. I just did 21 polls asking who should have a privilege re testifying about you. Each poll had 223-277 responses. Here is a table of the 21 options, a 1/0 depending on if law today gives such a privilege, and sorted by the difference between the Yes and No percentage responses:
Items in red are those where the law and the majority of respondents disagree; they agree in 69% of cases. The differences: majorities think parents and children should get privilege, and these folks who now have it should not: accountants, blog authors, and government officials. They are evenly spit on newspaper reporters, who now have it.
I’m not sure I see a good rationale for these limitations; this seems more to be about giving official respect and recognition to key relations.
If you do a follow up, could you apply the same idea re: confidential info to family/friends/contacts etc? For example, ask if your lover testifying could say that their testimony would have major consequences in a manner unrelated to the case.
Also, maybe check if their are any age/status/wealth correlations since I suspect there could be some minor factors that sway people e.g. younger people may be more inclined to view blog authors as high status.