Earlier quoted context omitted.
You say that Tinder reduces the "time investment and biological risk" of [sex]. I'm not a Tinder user, how does it reduce the biological risk? wouldn't the risk of an STD be just as great, if not greater, than the status quo?
More Sex is Safer Sex, according to economists, apparently: http://www.sld.cu/galerias/pdf/sitios/revsalud/more_sex_is_s...
The idea that non-promiscuous people having more sex can reduce STDs is more that the risk to a person having sex is lower, the more non-promiscuous people are options for them. Which is true - if only promiscuous people are looking to have sex with you, then every sex act is more risky.
But the risk for those non-promiscuous people goes up the more sex they have.
STDs exist that are like vampires in modern entertainment - once you become one, you are one forever, and you have a chance of turning others into one as well. Vampirism therefore spreads without limit, and so do STDs, if enough people have sex, for STDs that are incurable are not entirely preventable by condoms.
If people are having a lot more sex due to Tinder, as the anecdotes suggest in this article, there is no doubt that we will see a surge in STDs.