As the Poynter Institute notes, lawsuits against bloggers are on the rise going from four in 1997 to 89 in 2007. While the number seems small - it's a disturbing indicator of what will likely be a rapidly-increasing trend as advertising revenues continue to decline and the mainstream media is increasingly unable to return the higher profits demanded by stockholders (forcing staffing and budget cuts to news departments).
Corporations, having lost their bid to turn the Internet into a medium like the conventional media (where wealth controls one's level of access) by overturning Net Neutrality, are invariably going to seek out alternatives to preserve the control they exert over the traditional mass media. That means lawsuits; and frivolous lawsuits at that - knowing that bloggers lack the legal protections afforded to journalists do (being shielded behind the masthead of a newspaper that can afford to fight off "junk" lawsuits alleging defamation or copyright infringement).
This is one of several major hurdles to "citizen journalism" being able to take over in the wake of the declining quality of the mainstream for-profit news media. Another hurdle often cited is the lack of formal training for most bloggers (who do not frequently observe the standards journalists do which are designed to preserve objectivity in reporting).
It will be interesting to see what happens as this trend worsens. Will citizen journalists band together to form a consortium (which might maintain legal protections for member journalists who pay dues and agree to adhere to a certain set of standards)? Will legislation be introduced (or will case law be interpreted) that grants bloggers immunity from this sort of suit? Time will tell.
Regardless of the outcome, it will be interesting to observe what happens - and it will bear directly on how the First Amendment is interpreted in the forseeable future.