Or they (team members) need someone to keep pushing?
Edit:
It's less about pushing and more about planning the way forward. Somebody has to figure out what order things are going to be built, what the dependencies are, what resources are needed, etc. If it's not done by a dedicated project manager then the team will have to do it themselves.
It's possible.
It's just not very likely.
However a bad PM can definitely prevent a team functioning predictably and delivering on time.
You may not need a project manager as an exclusive role (depending on the size of the project in question) but you do need someone to track activity and make sure everyone is reaching their objectives, and assign extra resources to bottlenecks. In a large project, this is a full time job, and you would need someone just for that. In smaller projects, one of the team members can do this in addition to their other contributions. Of course, the project manager is, in fact, a member of the team, but I assume by team members you refer to the computing group.
I think it's likely the team will arrive at a destination, but with no acting PM or PM, who knows what that destination will be.
The PM keeps people on target, on schedule, and then adjusts when the target moves and the schedule is missed. Relying on a team to group communication is probably destined for trouble in more cases than not.
Its definitely doable, if you have a team that self polices itself. I've worked on projects where the team seemed to be more in tune with the time lines than the manager...
Also, I'm sure that there are plenty of examples small/medium size open source projects that get released without an official project manager.
Can they: Yes certainly. There are particular personality types that will work on time with little or no supervision.
Is this a good idea: Probably not. The type of people who are going to function at a high level in this type of setting are very few and far between. Once you have more than 2-3 people working on a project you will start bringing in people who need supervision. At that time a) one of the programmers will become the defacto project manager, b) the person will not contribute to their full potential or c) you won't ship :)
depends on the team, and how they work together
i've worked with agile teams that self-organize, mutually-motivate, and deliver promptly, all with no project manager
i've also worked with teams that had project managers, business analysts, quality assurance teams, network administrative teams, database administrators, et al, that delivered late and with less than optimal quality - mostly due to the "can't say no when the client is your boss" factor
It depends on who are the members of the team. If the team is filled with newbies or bums there's no future for the project, but if it's got motivated programmer who are focused and respect their goals, they can deliver more than what's expected.
Take Jo Peabody for example, he employed a team of programmers, let them run amok and earned some million dollars (At least that's what he claims in the book he wrote after he became a millionaire from Tripod). The book was 'Lucky or Smart'
So like I said, it depends on the team.
Yes, at least to some degree, as I explained in my recent Meeting-avoidance for self-managing developers conference presentation.