I think a lot of this comes down to the company's ability to vet a candidate. I find it fortunate that I can easily find and read code that someone I am interviewing actually wrote. In most cases you can also find when he/she wrote it and in what context. This is what I am looking for, and I don't need to get it from github or the like.
Job postings are more often than not (imo) poorly worded. The main idea is that you extract what they are actually looking for, which you can in most cases. If they ask for your github account and you do not have one - tell them you don't and send them some significant code samples. If they ask for a twitter/SO account and you don't have one - say you focus most of your commentary on HN and give them your username here.
I don't know of any companies that will ignore/discount you if you provide them with the data they are seeking.
Job postings are more often than not (imo) poorly worded. The main idea is that you extract what they are actually looking for, which you can in most cases. If they ask for your github account and you do not have one - tell them you don't and send them some significant code samples. If they ask for a twitter/SO account and you don't have one - say you focus most of your commentary on HN and give them your username here. I don't know of any companies that will ignore/discount you if you provide them with the data they are seeking.