Alerts won't send you the data (the story), but the metadata (information about the story, plus the link). One advantage of this approach is that if a site is deleted, making it vanish also from Google Search, you'll still have a record of it with enough metadata to pursue leads.
Note that Google also offers Google Scholar Alerts, which works like regular alerts but that searches academic books, papers and other resources. This is one of the great underappreciated services on the Internet.
You can also spy on yourself NSA style by capturing the metadata on your phone calls and chats. (Of course, the email is already there.)
The trick is to use Google Voice, and turn on the features that save your information to email. (Note that Voice will send your data to any email address, not just a Gmail one.) You'll find the appropriate checkboxes under the Voicemail & Text tab of Google Voice Settings.
This will send metadata on all of your calls, plus full data on all your SMS chats, transcripts of your recorded calls and voicemails and even the sound recording of your voicemails for searching later.
Note that Google's new Hangouts feature, which is accessible in Gmail, Google+ and in the dedicated Hangouts mobile apps, will send the full text of all your chats plus metadata on your video calls to the Gmail address associated with your Google+ account.
You can also use various tools like IFTTT or Zapier to automatically drop all content or metadata from any RSS feed into Google Drive, or alternatives like Evernote for searching later on.
Remember: Do it the NSA way and go nuts with this, dropping dozens, or even hundreds of items per day into your searchable storage. Don't worry about having too much data. Have faith in existing and future search tools to later find what you're looking for.
Beyond the automated harvesting of data, don't forget the manual approach, either. Capture every document that might someday be relevant and dump it into a special folder in Google Drive by using a browser extension like the Save to Google Drive plug-in. (Chrome has other extensions and so do other browsers.) You can do similar one-click saving using Evernote Web Clipper.
Once all this data and metadata is pouring into Gmail and Drive, you can simply use Google's search features to find what you're looking for.
The key to great NSA-style data harvesting, by the way, is to constantly tweak your code. Keep adding, deleting and modifying your Google Alerts and RSS feeds to make sure they deliver the kind of data you want.
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