Joe Biden was one of those who unmasked Flynn during the investigation. Biden was just on the air first denying any knowledge of the investigation and then saying "I was aware that...they asked for an investigation, but that’s all I know about it." Unmasking is fairly uncommon...

...Numerous Obama officials demanded the unmasking. Notably, the testimony of various Obama officials was recently released showing that every one said that they never saw any evidence of actual collusion with the Russians. Yet, the media is dismissive of the implications...

...Unmasking is more routine for intelligence officials but the involvement of figures like Biden magnify these concerns. This was an investigation into figures associated with the opposing party and incoming Administration. These were political critics of Obama and Biden.

It should be a matter of concern that the Obama Administration conducted such surveillance and investigation of the opposing party with no strong evidence of collusion. The unmasking requests only magnify concerns over the use of national security means for such investigations.