I recently started a new site and have sent quite a few backlinks to it (including from a number of web 2.0s that I manually created with unique content), but when I check ahrefs or WMT I only see a total of ten referring domains, despite the fact I've sent backlinks to a number of sites over the past week and a half or so. Is it just that Google takes a while to crawl pages depending on popularity (I notice that one backlink i managed to post on an alexa rank 100k site was counted within a day), or is there something else?