Snap (SNAP) is up 7% today on news of new ad products and stealing an AI expert from Facebook (FB), but the market is missing the clearly negative user numbers. According to data from SensorTower's Store Intelligence, Snapchat has seen a decline in downloads. For the first 10 days of May, Snapchat installs declined 28% to 6.2 million. The social service is going to have a difficult time growing the user base with lower installs while Instagram is growing installs. Investors shouldn't be paying up for Snap with weak user growth. More research: Snap's Earnings: One Ugly Quarter. Disclosure: No position