I see this often.
The profile for William Stone contains many sections taken as copy & paste from the work of Jack E. MacDonald.
Each time, there is a citation at the end of the paragraph, but nothing to let you know it is a direct quotation - no indentation, no quotation marks, no blockquote tags (recommended).
One section, 1628 Stone Settles on Eastern Shore of Virginia, does have quotation marks (and even the footnote number).
Then we get into the problem area. For Decision to Leave Virginia, see page 19 of MacDonald. Negotiations with Maryland picks up the next two paragraphs. Immigration to Maryland is the next paragraph (still page 19). Conflict between Maryland and Puritans is the first two paragraphs of page 20. 1655 Battle of the Severn still on page 20. Residence in St. Mary's City next paragraph on page 20. Will and Death the first line is original, then the next paragraph is a copy of the last paragraph on page 20. Then there is the Unsourced Statements section. Chances are some of that is Copy & Paste.
No blame. This stuff just happens. One person grabs it, thinking they will edit later. Another cleans up after a merge and removes quotation marks, or indentations ... on and on.
So, back to the original question, is this plagiarism?
* MacDonald, Jack E., (27 February 2014) The Stone Family of England, Virginia, and Maryland Part One. (http://freepages.genealogy.rootsweb.ancestry.com/~jacmac/stonefamily.pdf) Pages 19-20.
Edit: 16 July 2016 - added blockquote tags to copy & paste