There are many grey areas when dealing with plagiarism. Personally, when I write a biographical article I end up sifting through 4-5 online obituaries and merging the contents without much paraphrasing. Much of the information in those sources is second-hand and often equally unreferenced.
Where does one draw the line? When there is only one good-going source of material and this is paraphrased extensively, it should be referenced. There are many instances, however, where using the term "reference" would be a bit of an overstatement.
JFW