efax security holes

The biggest concern should be that your faxes are stored at someone else's server. Despite the assurance given by companies, I would highly doubt that files are not kept on their servers, once delivered. Additionally, there is no assurance of a bored employee at the premises going through the faxes, just for the heck of it.

Essentially, the biggest concern is loss of privacy. In addition, you concern level shoul;d be directly proportional to the sensitivity level of the documents. When e-faxis viewed, a little tool / utility is installed on the recepients machine, without their knowledge. This, in itself is enough to raise flags, since any knowledgeable person can send a simlar utility disguised under e-fax, and place a trojan on the recepient's computer.

I hope this answers your question.