I have heard both good as well as bad things re: Care.com - mostly negative however.
One important thing to keep in mind re: Careā¦..+ other online childcare websites is that ANY and EVERYone w/access to the Internet can post online, claim they are a professional Nanny, w/however many years of experience they want, etc.
It is like finding a Nanny on Craigslist.
Also the background checks may be shoddy too.