Concerns have been raised about a new website that lets people post their thoughts on care providers in England.
The Good Care Guide aims to give relatives a place to go to share their views on the service they have received from care homes and nurseries.
Government watchdogs helped develop the scheme but critics say firms could be put out of business if damaging posts are published.
Its backers say it will provide "real, honest feedback on what is available".
The guide gives people the opportunity to rate 60,000 care homes, home care, nurseries and nanny agencies in England.
In December, Care Services Minister Paul Burstow told the BBC the website was one of a number of plans to "shine a light on bad practice".
But Sheila Scott, chief executive of the National Care Association, told the BBC: "If a care home is ruined by a malicious comment, which is conceivably possible, then it's not just our member and their staff but the vulnerable people who are put at real risk, so that's our concern."
'Drive up standards'
However, parent Anne Vaughan told the BBC: "It's just another source of information, that's information that's not actually available anywhere else.
"It's as if you've gone round the parents of a particular nursery and spoken to them and asked them what they thought of it, which you really couldn't do even if you were visiting the nursery.
"You'd just have a look round, you wouldn't get any idea of what the people using the nursery actually think of it," she added.
The website allows people to rate providers for quality of care, facilities and value for money, and works in a similar way to the TripAdvisor travel website.
The website, which is run by two companies - My Family Care and United for all Ages - is designed to "help drive up the standards of care due to greater scrutiny".
Government watchdogs Ofsted, the Care Quality Commission (CQC) and a number of charities helped in its development.
Stephen Burke, director of Good Care Guide, said: "Families have been very enthusiastic about Good Care Guide. Clearly they want to express their views about their care provider. Some 80% of comments have been extremely positive, particularly about childcare providers.
"Good providers of care have nothing to fear about Good Care Guide but there are some families who have had bad experiences of care homes in particular."