Recently some OS X users have experienced problems in which their contact lists end up getting a number of No Name vCard entries. When this problem happens, these entries seem to accumulate over time to the point where thousands will fill the Address Book. In addition, the entries also show up on iOS devices that are being synced to the Mac.
One user on the Apple Discussion Communities suggested the issue may be from a MobileMe server error, as he was informed of by MobileMe support, so if you are experiencing this issue you might try contacting Apple's support to see if the issue can be rectified on their end. Apple is likely very busy getting the new iCloud services up and running, and there may be some odd problems that could affect users here and there.
Beyond contacting Apple, you can try resetting contacts sync data on your devices. To do this, first pick a device to be the new master device for your synced data, and set up the address book contacts as you would like (i.e., removing various No Name contacts and other duplicates). Then go to the MobileMe system preferences and click the Advanced button under the Sync tab. When in the advances settings click Reset Sync Data and choose Contacts from the drop-down menu. Then be sure to select the right arrow so the contacts are synced from your system to MobileMe, and not from MobileMe to your system, and then click the Replace button.
After the initial sync is completed, try syncing with your various devices, optionally removing your contacts manually from them before syncing to ensure that they are as bare as possible before importing the new list of contacts from MobileMe.