Many Sonic fans do not seem to approve that type of artwork but there seems to be also many of them who do not care.
Known sonic hentai artists are Kio, Toyjo, BbmBbf, Zeta R-02 and the list is growing as the game becomes more popular and there is more demand for sonic hentai.
Aku Toyjo is said to have quit drawing sonic hentai because of his art being stolen but there are some hints that show that he takes commissions and stays in the background.
Most of the artists' works can be easily found with a Google search.
Also a Sonic hentai doujinshi (comix) called Furry Bomb exists that is the most popular comic along with Sonic XXX Project from BbmBbf.
Current Furry Bomb issues are 1, 2.5 and 3 where there is known of a new rare 4th issue.
Finally there is a sonic hentai game under development called Amy Xtreme Adventure from Kio and expected to be released next year(2007) along with his new website.