Debian developer clarifies Mono position
The situation, according to Tolimar, is complex and he points out that Tomboy is currently a "recommended" package which he calls a "weak dependency" which can be removed later. The change being discussed by the developers is to add a "hard dependency" on a note-taking package, be that Tomboy or gnote. The posting makes it clear though that no decisions on the future packaging of Tomboy and Mono in Debian's numerous variants of install media (net, CD, DVD, BluRay and a range of desktop environments) have been taken beyond considering that dependency change.
Tolimar points out though that if a user installs GNOME with Debian, then there is a likelihood that Tomboy will be installed. But rather than "Debian will install Mono by default", he believes the more accurate statement is "Debian might install Mono with its GNOME install media, but that can still change".