How many people are behind the popular instant messaging programs
namely Yahoo Messenger, and MSN Messenger. I'm interested in knowing
the number of programmers that it takes to develop an instant
messaging program, as well as an estimate amount of monetary resources
it took to develop it, not taking into account the aquisition of
hardware costs.

The number of people to develop will basically depened on the time
constraint if u want it done in like an year a team of 100 divided
will only be nessesary longer less people shirter time more people its
not a fixed number as such it will basicaly depened on your buisness
or developmental strategy

about monetary resourses if its volunteer based u can actualy get it
done with very little money. If your thinking of seting up a new
messenger system its a suicidal mission because until or unless backed
by super sized media and advertisment power u wont even be noticed by
the majority and most people using msn and yahoo are more or less
satified by the surveys done till now , otherwise ushould be offering
something revolutionary which they will happilly mimic in a few months
if not few days.

and more money has gone into marketing them than development

Thanks vrn_25. I'm actually writing a report that compares big name,
big budget corporations to smaller companies, and I'm trying to gauge
their productivity, in correlation to the amount of manpower in the
team. Smaller companies could perhaps develop a product similar to
Yahoo Messenger with, say 10 dedicated programmers on the team, in a
short amount of timeframe. I'd like to know somewhat more of an exact
number before I can make this comparison. And of course, it would be
interesting if yahoo/msn did spend big bucks to hire additional
resources to reach a specific target date.

And I agree that most of the money has gone into marketing. That's the
main differentiator between a succesful product and one that is not.