The main con is fear of corporate lawyers if they think you're portraying them negatively. I am not a lawyer (nor a writer or publisher of fiction), but my impression as a reader is that minor mentions don't provoke their wrath but if your plot hinges on, say, a horribly-malfunctioning vehicle, you might not want to name a brand.
The main pro, on the other hand, is adding detail. "She fired up the search engine" is bland. People don't talk like that. (People don't talk like that so much that companies like Xerox and Kleenex have had to vigorously defend their trademarks to avoid losing them to common usage.) Using a name is one way to add detail.
That said, it's not the only way to add detail and it might not be the best way. Consider the following examples:
Joe got a cola from the vending machine.
Joe got a Coke from the vending machine.
Joe took the can from the vending machine, opened it, and took a long drink. Ah, he thought, just what I needed -- cold caffeinated carbonation. This should help me stay awake in my next class.
In this example it doesn't really matter if it's Coke or Pepsi or something else. The brand isn't important to the story; you were only reaching for "Coke" because most people don't talk about drinking "a cola". But you can show what's important about his drink without actually saying the brand; you get the richer detail and nobody who owns a trademark has grounds for complaint. (Though in this case it seems unlikely that Coca-Cola Inc would object.)
Granted, the last option is longer. This won't always work. And once you've introduced it, you can be terse in future references. In your example it might be just fine for Bob to drink "a beer" if you've already placed him in the bar. There isn't one approach that's always best; context matters.