Hello guys! I need your help again!

"There are several reasons why MySpace rates are lower. Some advertisers are reluctant to be associated with the freewheeling site,
which has
concerned some as a potential hunting ground for sexual predators."
"which" refers to
MySpace
"some" refers to
advertisers
Is it correct to understand the original sentence
"
...which has concerned some as a potential hunting ground..." as
"
MySpace has concerned some advertisers as a potential hunting ground."?
What confuses me is the word "as", which makes me think that advertisers are potential hunting ground, not MySpace.
Can you make up another sentence in the form of "A concerns B as C"?
Any help would be appreciated!

The entire article:
http://www.businessweek.com/technology/content/jun2006/tc20060616_682547.htm