Usually, familiar icons like TikTok, Snapchat, and Instagram occupy the top of the iPhone App Store, but not today.

According to Sensor Tower tracking, the top spot is currently occupied by two investment apps: Robinhood and Coinbase; TikTok, YouTube, Snapchat, and Instagram must occupy positions 3 through 6.

The situation is similar in the Google Play store. Here, Coinbase is sixth, Robinhood is seventh, and the top slot is occupied by Zoom, which likes various free games and video calls.

To be clear, Sensor Tower's rankings track momentum, not total downloads, so that the chart is more responsive to the movers and shakers of the app world. But even with this caveat, the breakthroughs of Robinhood and Coinbase are quite surprising and reflect the sudden fervor for casual app-based investing that has taken the Internet by storm in recent months.

Robinhood made waves in January when the r/wallstreetbets subreddit became the center of a so-called "meme stock" boom that drove GameStop shares from $17 to a high of $347.51. The boom temporarily restricted Robinhood from trading certain stocks and pushed many into alternatives such as Webull (#73 in Sensor Tower's rankings).

At the time of this writing, GameStop shares are at a much lower level of $154.69. But it is still up 810% from its initial value; certain users of R/wallstreetbets are trying to boost the value of AMC Theatre Chain, Bed Bath and Beyond, and the struggling BlackBerry Corp.

Coinbase is a bit simpler, a cryptocurrency trading platform that aims to simplify the process of buying Bitcoin, Ethereum, and Litecoin. Bitcoin has recently hit over $64,500 per coin, so there is no doubt about the popularity of this app.

While there is no direct connection between the two apps, the fact that their sudden burst of popularity occurred at the same time is probably no coincidence. Both allow inexperienced investors to turn small amounts of money into larger ones in a short period of time. For experienced investors, such volatility is a red herring, but recent success stories in cryptocurrencies and meme stocks mask the greater risk of losing everything. Social media apps, which usually occupy the top spots, do not carry that particular risk, despite their shortcomings.

If you're tempted to download Robinhood or Coinbase, our advice is clear: "If you're not sure you're ready to download Robinhood or Coinbase, you should consider it.