The practice is highly discouraged in alt.cybercafes. An exception is if you provide appropriate information to the group and include a link to your business. Collecting email addresses for SPAM is also discouraged. This is inappropriate and rude. Don't do it.
Discussions are welcome but insults are beyond discussion.
You are communicating with strangers here. If you wouldn't say something to a stranger on the street, chances are that it is inappropriate here. Criticizing someone for asking a question is also considered a personal attack. The posting of personal email to a newsgroup is also considered a personal attack and is unacceptable. Do not post binaries in a non-binary newsgroup.