Punctuation, spelling, proper grammar are just a few of the things we are losing to the texting/twitter influences. Cursive writing is now used for code. I miss the old days in many areas.
When it comes to bumper stickers, sometimes it's not punctuation but location. Take those 'Run, John Doe, RUN!' election stickers; if you support the candidate you place the sticker on the back bumper, if you support the other party you put the sticker on the front bumper.
Problem solved.
Two other good ones:
The fact that no one understands you doesn't mean you're an artist.
I'll believe corporations are people when Texas executes one.
Two that I embrace... God created few perfect heads. The rest he covered with hair. Honey, this isn't bald...its the solar panel for my SEX MACHINE!
(SWMBO responds, "Put on a hat, stay out of the sun, & get over yourself!")