What about Justin Carter, a 19-year old recently freed on $500,000 bail for another Facebook post?
So we know that Federal (and State) law enforcement spends resources following up very tenuous leads.
As far as burning sources and methods, what else would you have them do to follow up on this specific lead? Six agents interviewing someone for an hour seems less expensive than weeks or months of surveillance.
What does it matter if the account is true or false? It's completely plausible.