Not particular to any one strain of bipolar disorder, hypomania attacks people with both bipolar I and bipolar II versions equally. While the DSM requires a week long sustained intensive mania for a Bipolar I diagnosis, many Bipolar I and rapid cyclers (those who quickly alternate between manic and depressive states) experience hypomania on a regular basis. For many with bipolar disorder, moods exist on a continuum rather than sharp gradations of emotion and experience.
Lithium and other antimanic medications cannot cancel elated moods completely. To say that hypomanic delusions are less dangerous than full blown manic delusions understates the many ways in which disordered thinking can destroy. An irrational and false romantic attachment fueled by attraction to taboo and risky relationships, though relatively benign compared to suicide, nevertheless severs healthy friendships. Many times, disordered thoughts discovered in the depths of profound mania reappear in hypomania, perhaps attenuated yet potentially just as destructive and rarely less painful than severe mania.
Many times non-bipolar people enjoy the company of the hypomanic. Rattling on about obscure academic topics, the pleasantly buzzed and witty person across from you may perceive his world crumbling. Though an ignorant observer might easily categorize hypomania, the hypomanic knows how far she must step before smashing an observer's tidy definitions.