Yes, a big one, as the article explains: if you have a massive number of old people living on pensions / versions of social security, but not a lot of younger people working to produce goods and services, those old people are not going to be able to survive at the standards of living they'd like and b) over-taxed young people are going to be incentived to not work or leave.

These are not good things, especially because they have recursive aspects, as discussed.