SAN FRANCISCO -

Someone's dropping envelopes full of cash across San Francisco, causing a social media frenzy.
   
The mysterious person with the Twitter handle HiddenCash has been hiding money throughout the city since Friday that's leading scores on a scavenger hunt.  His Twitter following has exploded from a few hundred on Friday to more than 75,000 and counting by Tuesday.
   
Hidden Cash's creator says his giveaways are a "social experiment for good." He claims to make his money off San Francisco's hot real estate market and hopes that winners also pay it forward.
   
Adam Wenger, a 27-year-old web producer, said he won $200 finding two envelopes Friday in the city's South of Market District. He bought pizza for his co-workers on Tuesday and will pay a $100 parking ticket.