I agree 3x your income may be too high for many, depending on your circumstances and other debts. For example, a young professional or newly minted medical doctor may have a significant chunk of debt in terms of student loans. Young parents may be saddled with alot of expenses related to raising small children, etc. Likewise if you have significantly higher income/assets later in life you may be able to handle more housing debt relative to your income.
For first-time buyers I would assume most could handle somewhere in the range of 38-38% of their income towards the combination of debt and housing PITI.
