This can happen incredibly fast in linguistic terms -- anybody remember "e-mail"?
Since compounding words happens naturally in English grammar, hyphenation is some weirdo vestigial hangover from the times before English was written with spaces and the "rules" are entirely arbitrary and up to whatever style guide you happened to have studied in school.
In some bizarre twist of fate, hyphenation is on the decline and instead of just compounding two words together like any decent Germanic language, some style guides are encouraging people to keep the words separated with spaces, coming a full 180 degrees from the original use of a mark to compound words for clarity in texts made without spaces.
Is it "on-line", "on line", "online", how about "log-in", "log in", "login"?
It shouldn't go beyond notice that the hyphen seems to exist as a way to prevent compounding in the proper Germanic way, but isn't needed at all for Latin or Greek based compounds or neologisms.
Language prescriptivists can make a real mess of things and really screw the languages up for the rest of us. Trying to Romanize English was a terrible idea.