Over my years of teaching, I have memorized a couple dozen of these sonnets, on my morning walks. Some I learned in a two-mile walk,
like the one on his own writing, "Why is my verse so barren of new pride?"(76). Others I have had to re-memorize every time I teach it,
like "Some glory in their birth, some in their skill," (91). Their imbedded mnemonics vary greatly. When I have required Shakespeare classes
to memorize a couple, students would often pick very difficult ones, not knowing they varied so.
They only improve with familiarity as do many well-known poems. Ease of memorization is one criterion of poetic greatness, though it's also a function of personal experience and obsessions. Overall these sonnets may NOT be as easy to memorize as are Dickinson's poems, or many of WB Yeats's, say "Under Ben Bulben." Or Herbert's "Sweet day, so cool, so calm, so bright."
But as Will (his punning sonnet name for himself in the later ones) says of his own writing, "That every word doth almost tell my name" (76).
This can also be said of Dickinson's and some of Yeats's. Shakespeare adds that this verse name-telling also suggests the genealogy of the verse,"Showing their birth...." In that way, these sonnets become ads--for themselves. Political admen, eat your hearts out.