With the obligatory "I Am Not a Lawyer" out of the way, I should point out that in many places (it varies state by state) two-party-consent is not required. Two party notification is required. There can be some significant differences in some cases.

Again, far from an expert in law anywhere, but my understanding is that in most states you can go around in public openly recording conversations with no problems. The issue comes when you try to do it illicitly. A microphone that is obvious would cause no problems, but one that is concealed or otherwise nonobvious could be an issue.

If anyone really knows what they are talking about, I would be most appreciative for confirmation or correction.

As to how it should be, yes, I think that you should be able to record anything legally as long as the other party has no reasonable expectation of privacy (and yes, without their notification or consent as long as they do not then have a reasonable expectation of privacy). If you do something in a public place, you should assume it is being recorded. If you do something in the privacy of your own home or a bathroom stall, you should be able to do it with no fear of being recorded without your consent.

I know this begs the question of where we draw the line between public and private, but I think there will be little disagreement on most cases. Those fringe cases where there is disagreement I would tend to lean towards allowing recordings.

I think this should be true of all citizens, but I think it becomes especially important of public servants such as Police Officers whom the public has a right to demand accountability from. The Law Enforcement Agencies in America are fantastic, and I have the highest praise for them in terms of their performance and the effect they have on the streets of America. But they should never forget that they are public servants and (at least indirectly) accountable to the public in a Democracy.

IANAL. That said, I believe the relevant law is http://www.mass.gov/legis/laws/mgl/272-99.htm and the key element will prove to be whether using a cell phone as a video/audio camera would constitute a "secret" recording of audio as required by definition B4. (Apparently, with Glick's original case dismissed, there's a chance that it would not suffice.)

In terms of his suit, anyone can sue anyone for anything. It's the winning that's hard. I can't imagine any cause for action on impairing his freedom of speech, nor that sufficient probable cause did not exist to effect the arrest. While I don't like how the law is written, and may not agree with the premise, the law is the law and it's easy for an officer to believe that they have probable cause for an arrest under that law. Frankly, I think they had PC for the arrest, even as I wish they didn't and wish that even if they had, they'd have chosen not to make that arrest. I can't see how Glick can meaningfully win this case...

Interesting point. Where does "obvious" recording stop and "covert" recording begin? Can you break the law by simply having a high-sensitivity microphone?

And note the recent case of a man being charged with indecency for being nude in his own kitchen - but visible from a public place. So if anything conceivably visible/audible from a public place is now classed as "public", a laser mike on a window, or a zoom camera recording mouth movements (which can be reliably decoded into speech) might arguably be permissible.