Barbara Walker is of course highly respected in some quarters, and her writing did serve an important purpose at a time. This purpose, however, could be just as well served with less shoddy scholarship. Empowering women by telling them lies can work temporarily, but in the long run, it weakens the cause of gender equality.
I fear criticizing Walker a tad - criticizing such a widely cited feminist may seem as though I object to her feminism. I do not. I could of course write something dumb here like "why would I be anti-feminist, many of my best friends are women!", and although that would be true, it would also lead the discussion onto an irrelevant sidetrack. I maintain that shoddy scholarship is shoddy scholarship no matter what conclusions it reaches, and that shoddy scholarship indeed can be used to prop up any thesis: even the sciences have been supported by shoddy as well as good research.
At times, the scholarship in Walker's works is so shoddy, you do not even need to look up sources elsewhere: looking up the source she cites, you find it saying something quite different from what she says it says. An example:
Female soul, from the roots an, "heavenly," and ma, "mother," recalling a time when all souls were supposed to emanate from the Heavenly Mother.1 In the 16th century A.D. Guillaume Postel said every soul had male and female halves, the animus and anima. The male half had been redeemed by Christ, but the female half was still unredeemed and awaited a female savior2. This was a new development of the old Christian view that only males had any souls at all. The third canon of the Council of Nantes in 660 A.D. had decided that all women are "soulless brutes."3 [...]
1. Graves W.G. 410. 2. Seligmann, 223. 3. Dreifus, 4.
Graves' The White Goddess is a book that has repeatedly been republished ever since its publication - the copy I have borrowed does not have the same pagination. However, reading a few dozen pages and doing some simple arithmetics, I think I found the bit she is referring to here, on page 371 of the edition I have access to (bolding by me, not by Graves):
Ovid and Virgil knew their Goddess Anna Perenna to have been a sister of Belus, or Bel, who was a masculinization of the Sumerian Goddess Belili; so also the god Anu, of the Babylonian trinity completed by Ea and Bel, was a masculinization of the Sumerian Goddess Anna-Nin, usually abbreviated to Nana. Bel's wife was Belit, and Anu's wife was Anatu. Ea's wife, the third member of the Sumerian female trinity, was Dam-Kina; the first syllable of whose name shows her to have mothered the Danaans. Anna-Nin has further been identified by J. Przbuski in the Revue de l'Histoire des Religions (1933) with Ana-hita the Goddess of the Avesta, whom the Greeks called Anaitis and the Persians Ana-hid-- the name that they gave to the planet Venus.
Mr. E. M. Parr writes to me that An is Sumerian for 'Heaven' and that in his view the Goddess Athene was another Anna, namely Ath-enna, an inversion of Anatha, alias Neith of Libya; also that Ma is a shortening of the Sumerian Ama, 'mother', and that Ma-ri means 'the fruitful mother', from rim, 'to bear a child'. Here, Walker seriously fails at etymology. Graves does seem to get some etymologies right - even if he is barely a reliable source in the first place -, and he is less willing to go on far-fetched distant etymologizing than Walker is, but still - what she says he says, he does not say. Her etymology is not supported by her source, she is misrepresenting Graves. Her claim is a fabrication. Certainly an- and ma- are supported by her source, but only insofar as it applies to Sumerian and languages in close contact with it. Anima and animus, on the other hand, can be explained in part by recourse to normal Latin morphology - -a vs. -us being rather common suffixes for feminines and masculines, and the prior part being from Proto-Indo-European *h2enh1mos (PIE -os being the source of Latin -us as well as Greek -os), from *h2en(h1), "breath".
Further, the idea that the Catholic church ever has taught that women are soulless is a fabrication. Claims as to which council declared it varies, and no one ever gives a primary source. 
This is but one example of such a mistake, and I will post new posts as I come across major errors.
I do realize every encyclopedia ever contains mistakes and errors. Producing an encyclopedia is a monumental work, the effort required to verify every last claim probably infinite. This is a partial reason why using encyclopedias as sources is inadvisable. The example given above, though, is not relying on a mistaken source, it is misunderstanding the content of a source or misrepresenting a source - that is significantly worse, and indicates either that the author does not understand the sources or intentionally misrepresents them.
Acharya herself has this to say on encyclopedias, my emphasis:
Moreover, flipping through encyclopedias will not make an expert of anyone; thus, caution is required when reading hasty rebuttals from fervent believers—such commentaries tend to be inadequate, representing a cursory scan by those who are rarely experts. Such interpretations may sound impressive at first to the untrained eye; however, with serious, time-consuming research digging into long-forgotten and buried archives, most if not all of these shallow encyclopedia-rebuttals can be put to rest, as demonstrated in this present work.[5, A Word About Primary Sources]Many of Acharya's datapoints in the Christ Conspiracy and Suns of God are exactly that - shallow encyclopedia-factoids.
 Barbara Walker, The Woman's Encyclopedia of Myths and Secrets. I do not provide a page number, as the articles are ordered alphabetically.
 Robert Graves, The White Goddess
 Acharya S, Christ in Egypt