There are two types of sources here, the ancestry records such as census or bmd data and the links to family trees or millenium cd files.
You can usually rely on the link to the individual data records as being correct, even if you cannot see them yourself. It may be preferable to add open sources if you can so anyone cab check the facts.
The links to family trees etc. are often completly useless, they may give clues for further research but are not sources. If the profile has other sources or you can add better ones then these nonsources can be removed, in many case even people with more money than sense who pay ancestry cannot see the data supposedly a source as the file has been removed, or the data has changed and the profile has different data to the supposed source.