It doesn't use up too many resources, but I still don't like having more than 50% of the user database be essentially spam. If you ever want to sell your company you want to have somewhat accurate numbers of actual user registrations. Ever since I realised the extent of the issue I have become very doubtful about reported user counts from startups. In our case the only reason we've realised this is spam is because we annotate signups with GeoIP and also allow users to fill in a name and title which will then be something like "find escorts in Chennai" and the signup will be from India etc. If you only look at the email addresses all you'll see are many gmail addresses with western names, so you might be fooled into thinking that all of these are legitimate users.