I want to preface this post by saying I don't make a living performing genealogy research for others, and I don't claim expertise in a particular area of research or technology (although I like to consider myself pretty tech-savvy). I'm a long-time hobbyist, plain and simple, which probably colors my remarks a little.
I've seen a lot of Facebook posts and blog entries regarding "sharing." I'm using that term to cover a lot of scenarios: you connected with a long-lost cousin who wants your research; you post your tree on a website such as ancestry.com; abstracts that you may have done of original records; etc. Personally, I am willing to share any piece of information I've been fortunate enough to dig up. Along the way, I've run into a lot of very nice people who are of the same mind-set: pay it forward. I've had cousins send me packets of photographs and copies of original records they dug up through research trips. I've had perfect strangers take cemetery photographs for me. I was in contact with the widow of a man my mother corresponded with back in the 1970's, and she graciously sent me a copy of a book he had written. I've sent letters to small genealogy libraries and had volunteers make copies of obituaries from old newspapers. I've tried to return the favors, in small part, by volunteering through the Random Acts of Genealogical Kindness website.
I'm not saying that people who make their living from genealogy should give away their time and fruits of their labor for free. My point is that if you post information on one of the many websites such as ancestry.com, don't be surprised if someone lifts your research. Also, remember when others have offered you some small act of genealogical kindness, and try to do the same by paying it forward.