My Heritage trees offer users "Smart Matches" when matching persons are found. It is designed to help improve or fill in gaps in your tree. A recent match for me yielded some additional information about my ancestor Martha Horn (d. abt. 1761). (I am not citing the specific tree it matched because I do not wish to call out the person who placed the information online.)
The tree owner provided a middle name for Martha in her tree. Martha was born before middle names were common. The person also provided the middle name of "Asbury" for Martha's husband. Since Francis Asbury was not born until after my ancestor William, this seems rather unlikely unless William's maternal grandfather, or possibly a great-grandparent, bore the surname "Asbury." However, men born during William's time only possessed a single given name. I definitely do not want to add either middle name to my tree without good documentation.
The next reason I do not like to add smart matches relates to place name information provided. The individual provided a birth date for Martha of 1719. (I lack a birth date, but it seems a likely date since the youngest known child was born about 1740. I need better documentation before I add a qualifier such as "abt" or "est" to the date.) However, the birthplace given is Bertie County, North Carolina, United States. The last time I checked my American history books, North Carolina was a colony at the time, the Revolution had not been fought, and the United States had not been birthed in 1719. Bertie County (or Precinct) was divided from Chowan in 1722, so even the birth location is incorrect. The tree owner also places "USA" at the end of the death date, which occurred before the birth of the United States.
The tree owner provides parents for Martha. I do not wish to add those until I establish the fact through my own research.
I want to be fully in control of the data entered on my tree, and "Smart Matches" do not provide that opportunity. The default is that all new or improved information is added. While I like the idea of connecting with others researching an individual through some sort of confirmation, I do not want to be forced to accept their data in order to do so. Until accepting data becomes optional, I simply peruse the smart matches for clues, avoiding acceptance of questionable data. Of course, my tree at My Heritage is simply skeletal for DNA matching purposes in the first place. I like being able to see matching trees Ancestry without being forced to accept their data. I always ignore the trees, but I can still see those ignored hints if I click on hints. With MyHeritage, I want to be able to consult the tree but the only options on the review page are to confirm the match or reject it. At least by not confirming or rejecting the matches, I can still view the matching trees by looking at the pending smart matches.