I think it depends on the use that you need to do of the mongodb...
The reason of the wikipedia suggestion is that with mongoDb (until version 1.3.1) you couldn't make a backup without sopping the database first.
From 1.3.1 onward you can do a backup locking writes :
MongoDB v1.3.1 and higher supports an fsync and lock command with which we can flush writes, lock the database to prevent writing, and then backup the datafiles.
While in this locked mode, all writes
will block. If this is a problem
consider one of the other methods
If you have high usage of your application with many accesses deploying on two server it's the better way, whereas instead you have an application that is used only during the day, you could stop or lock the database, make a backup, then restart or unlock in the nightly hours ...