Marketers - if you were thinking of inventing an online persona to pimp your product, better think again. According to Adlaw, a law passed in Europe earlier this year makes it illegal.

The Unfair Commercial Practices Directive regulates unfair business dealings with consumers and outlaws “falsely representing oneself as a consumer". According to the buzz, that could make fake advertising blogs, to which companies post sales messages whilst posing as consumers for example, off-limits.

My untrained legal Spidey sense says that could mean last year's ill-fated Wal-Mart Across America blog, the UK's earlier Cillit Bang, pseudonymous Digg submissions, even postings to forums (some companies are known to hire students to do product placement on message boards).

Is this law enforceable? Yes, if a suspicious plaintiff can prove an online individual is not who she says she is. If that is the case, the EC may have just ushered in a new age of marketing transparency in one fell swoop.