background checks

Big online dating sites like Match/Chemistry (revenue USD 400 million), eHarmony (revenue over USD 250 million) have marketing expenditures over 50% of their revenues.
Background checks are going to be a minor investment for them, they can reduce marketing expenditures in USD 10 million and invest that money in background checks.

If the online dating site offers compatibility as strict personality similarity, it will be delivering to you candidates with nearly the same personality as you.
And if it has a high precision compatibility matching method, like the 3 persons most compatible per 100.000 screened, it can perform background checks as if you were an "employer" and the online dating site an "employment agency" showing you 3 prospective "employees".