I can't speak for the rest of you but I prefer knowing the people who make Safari extensions are accountable. Safari extensions have access to ALL the data on your webpage. That includes all banking and shopping data. Scary stuff.
This was posted earlier and is the venting about this issue by the developer of a rather popular extension.
They make the following point which deals with your concern:
In addition, spammers / malicious extension developers have a lot more than $100 to gain from publishing scammy apps. My Safari developer certificate is already linked / provided through my iTunes account ID (and therefore credit card etc), so it's not like the $100 gets them "more confirmation" that I am who I say I am.