[liviu-]

They are, as this link seem to indicate: https://wordpress.org/plugins/add/

>Currently there are 224 plugins in the review queue, 198 of which are awaiting their initial review.

[dr_hercules]

There are more than 38k plug ins available (https://en.wordpress.org/plugins/). And also from what I have seen so far - there is no extensive (if any) reviewing done regarding safety and quality.

[lucaspiller]

When you first add a new plugin it is reviewed, but once it's been accepted you are free to push out whatever changes you want without review.