If the text contains 2 consecutive URLS (separated by one space, or one newline), only the first URL gets linkified. This only occurs if the 2 URLs have the same format (eg, both with an http or ftp part, or both without).
Failing examples (only the first URL is linkified):
www.github.com www.google.com
http://www.github.com http://www.google.com
ftp://www.github.com http://www.google.com
But working examples:
http://www.github.com www.google.com
www.github.com ftp://www.google.com
www.github.com www.google.com (with 2 spaces in between)
Issue on Mozilla 6, IE8 and Chrome (didn't test other browsers).