I'm not sure there's a problem here. The article seems to imply the guy actually edited wikipedia home page to promote his client.
For what I understand of how "did you know" section works, it's not the case : it's automatically collecting recent additions (http://en.wikipedia.org/wiki/Wikipedia:Recent_additions/2012...).
It means that, worst case scenario, he only wrote a lot of new pages about Gibraltar. That's still an issue if those page are advertisement-like (which I did not checked if they are), but certainly not the same thing as spamming home page on purpose.
Also, he may as well have respected neutrality guidelines when writing those articles (even if it's a hard task, if you earn money from the person you're writing about).
The real problem is mostly : does others people have read those articles and checked them ? It's the good old wikipedia problem : only pages that attracts a lot of editors can be considered balanced enough, with or without PR, with or without money.