Genealogists rely on various sources of information to develop their family lineages and histories. Genealogists are always encouraged to document what ever sources were used from which information was taken, but not all sources are of equal value. The closer a source is to being contemporary with the events it describes (ie, births, deaths, marriages, family movements etc.) the better is its quality. A contemporary tax record documenting that a person paid taxes in a given place in a given year, is a high quality source---for the presence of that individual in that place at that time. Likewise, a church record giving the birth of a child to a particular set of parents at a specific place and time is a high quality source for the childs parents, DOB and POB.
The key feature of such sources is that they are contemporary to the events described. We may always misunderstand what a source tells us, and even contemporary sources can get it wrong (e.g., recordation error, where a date is accidentally miswritten, or mispresented.) But in general, contemporary sources are closest to the event, and have the best chance of giving us accurate data. More distant source may also be accurate, but they have a greater potential for mis-presentation.
Genealogist also make use of other types of sources that are more remote from the events, but still useful. For example, someone might write a letter describing what their mother told them of about their great grandmother. This is somthing the author does not know himself, but is simply passing on what he's heard. What he is told is probably true, but there is always the possibility that error has crept in. For example, he may not really understand what he's been told, and mistake the maiden name of one great grandmother for another. Perhaps he records what he was told accurately, but his mother misunderstood something about her grandmother, passing on an error as fact. The letter describing the information the author was given, becomes a family source. It is more or less accurate depending on the quality of information transmission. But no matter how accurate the source is, there's a greater risk that it contains an error, simply because its not contemporary with the events, and its content is subject to a higher degree of information loss and corruption. A useful source, to be sure, but it is still of lower quality than a contemporary record.
As information gets passed down, through oral tradition or through letters, eventually someone chooses to record their received family history. Perhaps they simply document it in a letter to their family, or perhaps they go further can present their information in book form. Typically such works will rely on a mixture of sources, ranging from contemporary records, to what amounts to hearsay. Others than can use this book for purposes of working up their own personal family history. The quality of such works can vary considerably, depending on how accurately and completely they describe their sources. The best works are those which give complete details about where their information is coming from, and back everything up with contemporary sources.
Ultimately, in this modern day, someone may take the information they have collected and place it on a web site. An advantage of this is that this makes their information more widely available, so others can benefit from their work. A disadvantage of this is that the works presence on the web is essentially ephemeral. That is, it does not persist beyond the time the person chooses for it to remain "up on the web". The significance of this is that eventually such ephemeral works are no longer available for others to examine. While that reduces its utility for those who come to the family history at a later date, it also reduces its utility for those who have previously made use of it. The reason for this is that once the material has been taken down, no one can revisit to verify what it had to say. Even if it was highly accurate, well documented, and of superb quality, its use is limited because eventually, no one can confirm what it had to say.
Ultimately, to be useful, a source MUST be accessible to others. If its not accessible, and can not be verified by others, then its value is greatly reduced. (See also: Verification and Validation.) Moreover, since web pages and the like are subject to change without notice, even if the material as a whole remains "up", you can't guarantee that the same information is being presented at a later date. Because the content of articles on WeRelate can be changed at anytime, they are, by definition, ephemeral sources. Ideally, articles on WeRelate identify the contemporary/original sources on which their information is based. Thus, while you can't necessarily use a WeRelate article as an indirect source, you should have (ideally) enough information to see where the information comes from, and be able to verify that source on your own.
On the other hand, since the "history" of any given article remains on WeRelate, and provides links to previous versions of an article, information contained in an earlier version of an article, but later deleted can still be examined. Should you need to make a reference to a WeRelate article, you need to specify the exact date on which you extracted the information. That will allow you, or others to retrieve the exact version of the article from which the information was extracted.