Cannibalization is when a company has several products that compete with one another within the same market.
This is naturally seen as disadvantageous, as a company will not only eat away at its market share for its own products but also on the total resources it has available for each of those product teams.
An advantage, however, can be to give the appearance of variety and choice in markets that are otherwise dominated by just a couple of companies. Some businesses also see it as an advantage to compete internally for the same customers, rather than with external competitors.