According to w:Hypercorrection, many German speakers mistakenly use the genitive with entlang. If that can be confirmed, a usage note would be helpful. Rod (A. Smith) 19:46, 5 July 2007 (UTC)
It's not hypercorrection at all. Duden says the genitive is the standard and most common case with the preposition. (Quote: "bei Voranstellung mit Genitiv, seltener mit Dativ, veraltet mit Akkusativ" .) To me personally only the genitive sounds normal after entlang (and I'm not someone who uses much of a genitive in normal speech). Anyway, the most usual form is postposition + accusative. ---- There is indeed frequent hypercorrection with gemäß and some other prepositions, though.