Google Alerts has seen some maintenance by Google's engineers recently. It added back the RSS option after losing it. There were also reports of the alerts not working for many.
In the past few weeks or so, it seems that Google Alerts have been increasing in activity. Maybe Google fixed something directly with Google Alerts or maybe it is related to the Google Hummingbird release? I am not exactly sure.
But I am personally seeing a lot more Google Alerts, as is one other person in WebmasterWorld. I do suspect others are as well but just not reporting it.
In fact, I see someone is attempting a negative SEO attack on my company web site:
Which one of you are at it?
Forum discussion at WebmasterWorld.