When i received my first invite i read what it was all about on their site...i found several things onthere wich made me decide not to join, sorry to all who invited me.
Some quotes from http://sms.ac/HomePage/termsandcons.aspx:
SMS.ac reserves the right to change the nature of this relationship at any time without notice to you.
Please note that your profile information will be publicly available to other users.
To promote community, we may facilitate interaction and communication between members. Additionally, if there appear to be common interests between you and other users (according to your profile information), we may send email or SMS messages that will introduce you to others or them to you. For this purpose, we may include your greeting and other profile information. For this community-related Service that is provided directly to your mobile phone, you will be charged.
YOU UNDERSTAND THAT SMS.AC MAY MODIFY SERVICES AT ANY TIME AND THAT SMS.AC SPECIFICALLY RESERVES THE RIGHT FROM TIME TO TIME TO ALTER THE NUMBER OF FREE MESSAGES AND OTHER FREE SERVICES OR ELIMINATE ANY OR ALL FREE OFFERINGS ENTIRELY AT ITS SOLE DISCRETION, WITH OR WITHOUT NOTIFICATION.
You acknowledge that SMS.ac doesn't pre-screen Content, but that SMS.ac and its designees shall have the right (but not the obligation) in their sole discretion to refuse or move any Content that is available via the Service. Without limitation, SMS.ac shall have the right to remove any Content that violates this Agreement or is otherwise objectionable. <<<
how do they know if they don't read your messages?
Your use of this service and interaction with other users is at your own risk. Your profile can be viewed by other users. You may receive messages from SMS.ac or other users at any time. View pricing per country at Mobile Commands Help
http://www.sms.ac/MobilecommandHelp/help.asp.