Carousels are effective at being able to tell people in Marketing/Senior Management that their latest idea is now on the Home Page.
They are next to useless for users and often "skipped" because they look like advertisements. Hence they are a good technique for getting useless information on a Home Page (see first sentence of this post).
In summary, use them to put content that users will ignore on your Home Page. Or, if you prefer, don't use them. Ever.
The answer seems to be, 'mostly ineffective for site users, but it depends'. Note that I emphasized site users. ;)
The answers are hilarious! Doubly so because they seem to be true.