Bitcoin (BTC-USD) and other major cryptocurrencies are falling on today (Wednesday), with bitcoin, Ethereum, Ripple, bitcoin cash, and Litecoin all displaying the red candle. There are two particular negative news items that could be weighing on the market today and here are the details.

Of the top 10, NEM (XEM-USD) is the only one rising today, continuing a multi-day rally. In fact, the digital currency is up by more than 43% over the past week on news that the Coincheck exchange has begun reimbursing customers affected by January's massive NEM-specific hacking incident.

Google bans cryptocurrency ads

Just last month, Facebook announced a new policy banning cryptocurrency and initial coin offering (ICO) advertisements, and Google seem to be now following in its footsteps.

Yesterday (Tuesday), Google announced its plan to ban ad content "including but not limited to initial coin offerings (ICO), cryptocurrency exchanges, cryptocurrency wallets, and cryptocurrency trading advice." The restriction takes effect in June and will extend to all of Google's ad platforms.

Effectively, this hinders cryptocurrency-related businesses from using two of the largest ad platforms in the world. While this is obviously intended to protect investors from scams and excessive speculation, it appears to be doing a lot of damage on the entire cryptocurrency market.

A new analyst note from Allianz Global Investors warns that bitcoin (BTC-USD) is worth nothing, even if blockchain technology continues to evolve.

The rationale? "A bitcoin is a claim on nobody -- in contrast to, for instance, sovereign bonds, equities or paper money -- and it does not generate any income stream." The note also said that bitcoin "ticks all of the boxes" of criteria for a bubble. And while the note was about bitcoin, it's fair to say that the logic would extend to other cryptocurrencies as well.

To be fair, I realize cryptocurrency investors are generally not swayed in their opinions based on the warnings of Wall Street types. Warren Buffett, Jamie Dimon, and Carl Icahn have all been just as negative as Allianz on bitcoin and other cryptocurrencies, and it hasn't done much to prompt speculators to sell.

However, notes like these could have an effect on would-be investors sitting on the sidelines -- this could make them think twice. Bitcoin and other cryptocurrencies, at this stage, rely on growing investor interest, and prestigious figures in the financial industry can certainly influence this growth.