The ‘weak point’ in linguistics?

No two speakers have exactly the same lexicon. My own active lexicon, for example, does not include ontological, because I’m not convinced I actually have a clue what the word means, but a philosopher friend uses it quite regularly. Some speakers have a bigger lexicon than others, though we need to be careful here not to confuse size of lexicon with breadth of standard language vocabulary – many people have an extremely rich non-standard or dialectal lexicon, but struggle to express themselves in a standard variety, and may find themselves stigmatized by mainstream society as a consequence.