I wanted to do my own research to provide those who might be tempted to throw these words out in casual assertions with some clear definitions and some tools you could use to perhaps determine if certain behaviors rise to the level of actual "harassment" or "stalking" before using those terms.
Many states, including my own, have passed laws where these terms have been given specific meanings that can help provide some guidance (although many I have seen are still problematic in an operational sense as they are fairly vague and do not differentiate between "annoying" and outright "harassing" behavior).
Let's start with a dictionary definition of harassment:
Okay, that is not very helpful in terms of distinguishing between behavior that is socially and morally acceptable from the abusive kind of behavior. What causes behavior to rise to the level of harassment vs. mere annoyance?aggressive pressure or intimidation
My own state of Washington defines an "unlawful harassment" term thusly:
California was one of the first states to pass online harassment legislation and this is their definition:"Unlawful harassment" means a knowing and willful course of conduct directed at a specific person which seriously alarms, annoys, harasses, or is detrimental to such person, and which serves no legitimate or lawful purpose. The course of conduct shall be such as would cause a reasonable person to suffer substantial emotional distress, and shall actually cause substantial emotional distress to the petitioner, or, when the course of conduct would cause a reasonable parent to fear for the well-being of their child.
The key distinctions of harassment over just annoying behavior are:"Harassment" means a knowing and willful course of conduct directed at a specific person that a reasonable person would consider as seriously alarming, seriously annoying, seriously tormenting, or seriously terrorizing the person and that serves no legitimate purpose.
- willful (speaks to the intent of the actions)
- directed at a particular individual
- seriousness or severity of the conduct (typically "torments" or "terrorizes" the individual)
- serves no legitimate or lawful purpose
- causes"substantial" emotional distress
Washington state's cyberstalking statute says:
So, my state differentiates cyberstalking different from plain harassment:(1) A person is guilty of cyberstalking if he or she, with intent to harass, intimidate, torment, or embarrass any other person, and under circumstances not constituting telephone harassment, makes an electronic communication to such other person or a third party: (a) Using any lewd, lascivious, indecent, or obscene words, images, or language, or suggesting the commission of any lewd or lascivious act; (b) Anonymously or repeatedly whether or not conversation occurs; or (c) Threatening to inflict injury on the person or property of the person called or any member of his or her family or household.
- requires a particular intent
- requires an electronic (but not telephone) communication
- requires the content to be of a nasty nature OR
- requires making a threat to the person or property or relations
But some of the actions that I've seen documented would appear to meet (IANAL) some (or more) of the legal criteria. Such as photoshopped obscene pictures of the individuals being criticized, and perhaps the practice of doxing people that you disagree with (which only seems to serve the purpose of intimidating the individual by exposing their physical and personal information).
Anyhow, the legal language still does not make it quite clear where to draw the line between annoying someone and harassing. Stalking may be clearer, although I don't quite understand how the term "stalking" applies based on the way the legal language is written. What is more useful is a heuristic tool to gauge someone's words and actions. One such tool was mentioned on a Linkedin discussion forum that is claimed to originate from the University of Alberta. I tried to find the primary source material for the tool as I think it is a good one, but have yet to find it. I will quote it here for posterity and will add pointers to the original if it ever comes to light. The tool is called R.A.T.E.:
I like that this model includes an assessment of the relative power of the individuals involved. There is a note that a single incident would not rise to the level of harassment. Harassment would generally need to involve a pattern of behavior.
- Respect - Is this behaviour respectful? Does this behaviour honour the dignity and the worth of the person? Does the behaviour recognize and appreciate differences - culture, viewpoint, age, status etc.?
- Appropriate - Is the behaviour appropriate to the situation and to the relationship between the individuals?
- Trust - Many relationships are relationships of trust - e.g. the relationship between a professor and student or between an employee and manager. Is the behaviour a violation of the trust?
- Equal - What is the power balance in the relationship? Are the individuals equals? Is the behaviour exploiting a difference in power? Would an objection to the behaviour threaten the well-being of the person to whom the behaviour is directed?
 "RCW 10.14.020 Definitions", http://apps.leg.wa.gov/rcw/default.aspx?cite=10.14.020, accessed 2013-02-18
 "PENAL CODE SECTION 639-653.2", http://www.leginfo.ca.gov/cgi-bin/displaycode?section=pen&group=00001-01000&file=639-653.2, 653.2. (c)(1), accessed 2013-02-18
 "RCW 9.61.260 Cyberstalking.", http://apps.leg.wa.gov/rcw/default.aspx?cite=9.61.260, accessed 2013-02-18
 "Harassment", http://criminal.findlaw.com/criminal-charges/harassment.html, accessed 2013-02-18
 "State Cyberstalking and Cyberharassment Laws", http://www.ncsl.org/issues-research/telecom/cyberstalking-and-cyberharassment-laws.aspx, accessed 2013-02-19
 "Where is the fine line separating "harassment" behaviour from merely "annoying"?", http://www.linkedin.com/groups/Where-is-fine-line-separating-4416291.S.152158149, accessed 2013-02-19