If you want to be a bad product manager, develop your plans for new enhancements on your own. You’re the manager of the product so it’s your decision what comes next for the product. Why would you need to discuss that with anyone else? Don’t bother talking with your sales staff about whether you could get additional revenue with the new features. Don’t check with marketing to see if they have the resources to support the promotional plan you’ve devised. Don’t talk with engineering to get estimates on how much it will cost and how long it will take. Don’t get input from user experience designers on the impact these new aspects will have on the usability and utility of your product. At some point you can figure those things out, but you don’t need to work those things out until you start working on the new enhancements themselves.

If you want to be a good product manager, involve stakeholders as you plan additional projects and changes. While you as the product manager should be the authority and have the decision about what the product should do, by no means should that be developed in a vacuum. Keeping stakeholders in the dark is a bad idea for three main reasons:

1. Input from other parties is essential to actually develop your plans. You may have a great idea for a change to increase revenue, but when you discuss this with finance, you realize the potential problems it would cause for accounting. Some functionality changes may seem very simple to you but may require significant technology rework behind the scenes. Your project plan may assume availability of resources that just aren’t available.
2. Stakeholders may (gasp!) actually bring good ideas to the table. Rather than assuming you know everything about what the product should do, ideas for enhancements can come from all areas of the business. Too often product managers assume that they are all-knowing and that everyone else exists just to deliver on their wishes. Good product managers know that some of the best suggestions may come from developers, designers, or support staff.
3. Involving others as you plan new enhancements is worthwhile if for no other purpose than it creates buy-in. No one likes being blindsided with this sort of email: “We just received funding for a new project that starts next week. I’ll need three of your people to start Monday. I can explain more later what we’ll be doing.” Keeping everyone in the loop is just a good management and leadership practice that product managers should follow.

As a product manager, you should work closely with others within your organization to plan upcoming projects and enhancements to get the appropriate accurate detail around your plans, obtain good ideas and suggestions from all areas, and increase the likelihood of buy-in and eventual project success. Keeping plans to yourself is a bad and short-sighted strategy that is bound to create problems and thus should be avoided except only in extreme circumstances.