The 50-year-old, of Liphook, Hampshire, was convicted of raping five women and was also found guilty of attempting to rape and sexually assault two other women after chatting to them online.
Sentencing Lawrance for the attacks between June 2011 and November 2014, Judge Dickinson said: "I am convinced that you are devious, manipulative and highly dangerous to women.
"Most if not all of the victims had not tried to hide from their families and friends that they were on a dating site - they had told them that they were meeting the defendant.
"It does seem to me consideration should be given to a system of automatic referral to the police or some other central agency of any complaint that is made." Judge Dickinson told the court - in which none of the victims was present - that no one person or organisation had been in a position to "join the dots" or have an overview of the complaints made to the website.
"My home is no longer the haven it was, with cherished memories of my late husband and children.