I guess "bite" could mean criticism, but if you read the rest of the paragraph it doesn't feel that way.
Of course, these tongue-in-cheek projects still have plenty of bite to them. Gmail’s Twitter account announced that 100,000 interventions were sent in the site’s first 24 hours, and that ‘Gmail Man’ video could help salespeople rekindle Gmail privacy fears that have largely died down over the last several years.
In this context, it's this meaning of bite
A powerful, effective, or exciting quality.
Examples - His novel lacks any real bite.
The fuel-injection system gives extra bite to the 24-valve engine.
So the article says these projects, though they seem innocuous and rather embarassing even, still have attractive characteristics.
I just stumbled upon this. Even though it is over a year old I thought it would be a good idea to clarify the answer a bit.
In this case "has a little bite left" is an idiom based on a metaphor, though I believe the more standard way to say it is "has some bite left".
The metaphor is to an aggressive animal: a lion, bear, wolf etc typically one that uses it's teeth in a fight. The picture is of an aging animal who once was one of the elite fighters. as an example, consider an alpha wolf. "Some bite left" suggests that while he is losing his strength, and thus his lead role is diminishing, he has enough strength left to hold on to much of his power.
