This recent article from the Ventura County Star tells the stories of some families with adult children who have moved home, or are considering doing so, because of layoffs and other economic troubles. According to the article:

For young adults in their 20s or 30s, moving back in with parents can create a power struggle around the young adult’s emerging identity, according to Dr. Debra Sheets, a CSU, Northridge health sciences professor who counts intergenerational issues among her specialties.

Younger adults are still marking their territory, but when you’re older, you’re supposed to be established. Moving back in with the parents holds a more negative social stigma.