One disadvantage that worm composting has to true thermophilic composting is that it does not kill seeds. So, if there are weed seeds, or seeds from the fruits that you have fed the worms, the worms will not kill them and they can end up still viable in your finished worm castings.
Fortunately, where there are worms there are worm castings, and where there are worm castings, there is plant growth.
Seeds in a worm bin will often sense the nutrient rich environment (try to imagine a better place to germinate as a seed!) and will germinate and begin to grow.
If the seedling cannot reach sunlight, it will eventually die, and then it will get re-composted into the worm bin.
If you really need to kill the seeds in your worm bin, the best methods would be to hot compost the material/kill the seeds some other way first before adding it to the worm bin (if you kill them after you'll also kill a lot of the beneficial stuff in your castings), or do what you can to encourage germination (warmer "soil temperatures and good moisture levels) before using the worm castings.