Alphabet's biggest bear on Wall Street breaks down the 2 risks he's worried about (GOOGL)

Alphabet just had its developer conference, where it explains the new technologies it's investing in.
One cutting edge technology is artificial intelligence.
Wall Street's biggest Alphabet bear, Pivotal Research's Brian Wieser isn't too hot on Alphabet's artificial intelligence business.
And he also thinks AI doesn't help advertising revenue grow, which he says is bound to decelerate.
Watch Alphabet trade in real time here.

Alphabet just held its annual I/O Conference, where it tells investors and analysts what new technologies it's investing in. The company gave investors the run down on how it's improving artificial intelligence and machine learning on its various user platforms like Gmail and Google Search.

But Pivotal Research analyst Brian Wieser, Wall Street's biggest Alphabet bear, told Business Insider he's skeptical of two key themes in its business: the company's artificial intelligence businesses and the digital-advertising market.

Alphabet's main artificial intelligence product, Google Home, hit the market in November 2016, but the company doesn't show much financial information on its artificial intelligence business, so investors can't be armed with information needed to make bets on its impact.

But Alphabet's AI business isn't just about selling new products. It's also used to enhance machine-learning algorithms on Google platforms. For example, Gmail can now auto complete entire emails through "Smart Compose."

But Wieser says those developments don't have much impact, and they aren't doing much to drive advertising dollars.

"These aren't material businesses yet," Wieser said. "It's so small relative to the rest of the business that it's barely worth attempting to model separately from the rest of the business."

His point about AI not necessarily driving ad dollars is related to a broader risk he warned of: a slowing digital-advertising market.

"The total ad market is relatively fixed, and the share digital can take of that market is relatively fixed, and so that yields a lower revenue growth from advertising than most people think," he said.

While Wieser sees a looming slowdown in global digital-advertising growth, recent data from Magna Global shows that market was $209 billion in 2017, up 19% from a year earlier. And 2017 was the first year in which digital ad spending beat television ad spending, taking 41% of the total advertising market. Television ad spending captured 35%.

Wieser's price target on Alphabet is $970, about 11% below where it's currently trading.

Alphabet is up 1.71% this year.