Utsab, I am very glad you included Possibility #2 in your guide, because like you stated, there are various conditions that can cause a database to be marked "suspect" and most people ignore this benign state in Possibility #2 that the database sometimes falls into when they document how to recover from the problem. Once SQL Server marks a db 'suspect' the worst is usually expected due to all the worst case scenarios that have been documented elsewhere and the fact that your database is no longer accessible, which tends to freak people out.
I have one server that had multiple production databases, but one db would get marked 'suspect' occasionally for just this reason. And the reason is evident when you look at the SQL Error log and you see that when SQL needed access, some other process had it locked. It was then marked as suspect.
The easiest way I found to recover in this scenario was to take the database OFFLINE (not detach!) and then bring it back ONLINE in Enterprise Manager. This worked very well in SQL Server 2000 and didn't affect any of the other databases in the instance. I haven't encountered this kind of suspect db in SQL Server 2005 yet.