There have been discussions of these robotic subscribes on this list in the past. Up until a couple of days ago, the ban_list or GLOBAL_BAN_LIST regexp '^.*\+\d{4,}@' i.e., any email address whose local part ends with '+' followed by 4 or more digits) has been effective at blocking virtually all of them I've seen.
Now there is a new pattern. So far all the new ones I've seen match '^[a-z]{4,}\.?[a-z]{4,}\+[a-z]{4,}@gmail\.com$'. Some examples are
dramaalertbiz+<letters>@gmail.com kemo.mart+<letters>@gmail.com kezukaya+<letters>@gmail.com killerkeemstar+<letters>@gmail.com leafylagann+<letters>@gmail.com newdramaalert+<letters>@gmail.com ooktap.yaylea+<letters>@gmail.com ubercoffeetime+<letters>@gmail.com
where <letters> is a string of 4 or more random letters.
-- Mark Sapiro mark@msapiro.net The highway is for gamblers, San Francisco Bay Area, California better use your sense - B. Dylan