As others have said, you aren't the first one with this idea. The typical way to make this viral is to send out a message to anyone picked that "someone has a crush on them". The problem with this is that this "crush" might just be somebody making guesses as to who has a crush on them. OkCupid actually changed their behavior recently to say who rated you with a 4 or 5 instead of making the user guess, likely because of this problem.
Not proposing this as an idea (I'm glad you're not doing this) but just throwing it out there so you understand different options and the consequences of this particular virality strategy.
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As others have said, you aren't the first one with this idea. The typical way to make this viral is to send out a message to anyone picked that "someone has a crush on them". The problem with this is that this "crush" might just be somebody making guesses as to who has a crush on them. OkCupid actually changed their behavior recently to say who rated you with a 4 or 5 instead of making the user guess, likely because of this problem.
Not proposing this as an idea (I'm glad you're not doing this) but just throwing it out there so you understand different options and the consequences of this particular virality strategy.