Registered user

I have been getting emails saying I have new registered users to my WordPress blog. Here is a copy of the latest email:

fromWordPress <wordpress@virgilcook.com>
tovcook1956@gmail.com

dateSun, Oct 25, 2009 at 6:37 AM
subject[Virgil Cook.com] New User Registration
mailed-bygator899.hostgator.com

hide details 6:37 AM (31 minutes ago)

New user registration on your blog Virgil Cook.com:

Username: IonitonSpeeli

E-mail: fghnhjfgh@rambler.ru

I have received several of these emails and I have found where these users are listed but I do not know why they are there and if I should communicate with them or what?

If you go into you wordpress dashboard under users and click on ‘Authors & Users’ I get a list of all the signups. See attached:

Users
All (38) |Administrator (1) |Subscriber (37)Search Users:
Bulk Actions Delete Change role to…Change role to… Administrator Editor Author Contributor Subscriber
Username Name E-mail Role Posts
Username Name E-mail Role Posts
alenkrusk

Edit | Delete ertrfhhhhhq@mail.ru Subscriber 0
anasttqq

Edit | Delete anastttqq1@mail.ru Subscriber 0
aniniurce

Edit | Delete cecelia.bennett2@gmail.com Subscriber 0
annamrysdf

Edit | Delete annamrysdf@babusya.com Subscriber 0
arterydut

Edit | Delete webmaster@seosearchengineoptimizationservices.net Subscriber 0

This is a part of the list. My question is, How are they registering as a user and should I be comminicating with them or not?

I would appreciate any help I can get. They do not seem to be hurting anything, but if they are signing in to get updates or more information I would like to respond without the chance of my website being compromised.

Thank you,

Virgil