The most important thing a product manager does is decide where their product stops and someone else's product takes over. If the product doesn't do enough, it won't be worth the cost of installation, registration, maintenance, let alone purchase. If it does do too much, it'll clash with some pre-existing software or workflow that is already well defined.
Des provides some great guidelines for where to stop.
You should usually stop your product when the next step…
- has well defined market leaders looking after it (e.g. PayPal, IMDB, Expedia), and you don't intend to compete.
- is done in lots of different ways by lots of different types of users (e.g. trying to process salaries in a time tracking app would be tricky)
- involves different end-users than the previous steps (e.g. managers, accountants etc.)
- is an area you can't deliver any value.
Can you think of examples which overstepped this boundary and failed because of it? What about the opposite? Products which broke the rules and yet took the market?