Too much vertical growth is injurious to health of employee and employer. Let’s try to understand what is vertical and horizontal growth of an employee; well if I hire someone for a particular function of my company and regularly promote him for the same function & increase his team size this is vertical growth, now horizontal growth is if the same employee is being assigned cross functional and cross departmental responsibilities consequently enhancing his skill sets this would come under horizontal growth. Monetary benefits would generally remain same in both the growth types. So how come too much vertical growth is injurious to health of employee and employer.
Let’s take employee perspective first, everyone should continuously gauge where he stands in the job market, what is his / her demand with respect to the skill sets acquired under the current employer this defines your Employability Quotient(EMQ not EQ because is EQ de facto acronym for emotional quotient). The second important thing is to gauge how much value you are giving to your current employer such that it’s tough to ask someone else do your current job this defines your Replacement Quotient(RQ). If your EMQ is high and RQ is low that means you are on right track in terms of organizational growth. Now too much of vertical growth would mean a generalist profile with little or no choice multiple skill sets consequently lower EMQ and higher RQ which means unsustainable growth within and outside the organization.
As for employer perspective too much vertical growth is likely to result autocracy, closed groups pursuing unjustified or blind favor ruining the harmony within team. Generally this will develop what I call venomous leaders who are incapable of rational decision-making as a result contaminate entire company culture. Bright people would always stay away from such organization so ultimately its employer who suffers. So employer should always strike a balance between vertical and horizontal growth.