Just another medium for meeting others I believe. Never actually tried it, do have two friends though who both met people on a dating site. One got married and seems really happy to this date and the other, after a few not so pleasent meetings seems to have met someone really nice.
You can meet people in bars, clubs, university, work even in the supermarket and just like dating sites the experience can either be positive or negative, successful or unsuccessful and sadly we can meet people who are going to let us down just about anywhere.
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The soul would have no rainbow if the eye had no tears