We place quotas on peoples profiles so they are more in line with statistics(Dating sites have an insanely disproportionate number of blonds, and an unusually low average weight for women. While men on dating sites appear to be much taller and collect much higher paychecks than the national average.) "Sorry sir but we dont believe you are 6 foot 6"
Another thing you could do is force people to upload scans of their drivers licenses(with important info blacked out). That way lying would be impossible. Plus, the drivers license would let you know what the person looked like on an average day and not when they put on a shit ton of makeup and take pictures from insane angles.