Having a common name can be quite tricky online, and takes advanced planning to make sure you dont get left with a bad choice for username. As 'Jon Williams', I try to be the first one claiming 'jonwilliams' in any new online system.
In the 90s and early 2000s when the online population was smaller, I was always successful. I got jonwilliams (at) yahoo.com, email.com, mail.com , excite.com and many other online accounts. I also claimed jonwilliams.com domain (which I dont use but own). But as the online population grew, my hit rate dropped. I missed jonwilliams (at) gmail.com and jonwilliams on Facebook, but I did get jonwilliams on twitter. On linkedin, I had to take jonwill, but no big deal as it only shows up in my public profile link - www.linkedin.com/in/jonwill . Since so many new online services become available weekly, I frequently find that jonwilliams is taken, most recently, jonwilliams on about.me . If about.me takes off, then I'll have to compromise with punctuation or numbers in my name!
Clearly, a single sign-on solution would solve this, but we still seem to be far away from this. Microsoft Passport was a colossal failure. Facebook has done a successful job of single sign-on, but I am not comfortable using that for accounts that may have my credit card. Google may become a standard here, but then I will be jonaussie (at) gmail.com everywhere.
I have some friends with unique single word name handles, like glemak or r0ml, but for me this would feel like I have decided to rename myself to sound like a new start-up (like jonio or jonwillr?). I feel sure this multiple account dilema will go away in the distant future, but for now, I'll keep claiming jonwilliams whenever I can!
... and my apologies to all the other Jon Williams's out there, I feel your pain.