I set up my google voice number to forward to my AT&T number, but when I get texts from some people who are in my contact list, the text appears to come from phone numbers I don't recognize. The text message itself will be prefaced by the phone number the text is coming from, but even though that number is in my contact list, the message does not offer me the name of the person. I have an iPhone 4 and I'm running iOS 6.1. Any help is appreciated.
This is, unfortunately, a limitation of Google Voice. Google Voice cannot spoof your friends' numbers, so it has to send texts from its own numbers. However, each of your contacts will have a unique number from which Voice will send you texts, so you can send messages to those numbers and reply to them and it will reach your friends.
There are two ways around this. You can use the Google Voice app. Messages will come through your data plan and not your SMS plan, and they'll show up with the right names and everything. Alternatively, you can add the numbers Google uses as the "from" address as another number in your iPhone contacts. The number will still work to reach them, and the messages will appear to come from your Google Voice number.
As google has shown in this link, this is a normal feature of Voice.
You have your Voice account set up to forward messages to your phone (from google). Unless you have a phone number at Google Voice, you will receive the messages from one of the random phone numbers that Google owns.
It is stated many times on the net that if you get the Google Voice app, it will show you the actual number of the sender; rather than the number assigned to forward the messages to your phone. This should eliminate the issue.
The problem is not a normal feature of Google Voice (nobody else has ever experienced it, to my knowledge, except the original poster of this question). It was not caused by Google Voice settings. It was not caused by Google Voice iOS app. It was not caused by Messages app. It was not caused by SMS GV Extension. It WAS caused by Google Contacts sync. I fixed the problem simply by deactivating Google Contacts sync on my iPhone and then reactivating it a minute later.
Please stop editing this answer to remove the important explanatory material in the blog post I wrote about the issue. You are not helping anyone by hiding this information.
The reason the texts come from a strange number is so that replies will go back through google and appear to come from your google voice number. If the texts came from the real users phone number, when you sms'ed back, it would be from your iPhone's phone number, and not from your GV number on their side.