Brad, ultimately you have to weigh the time involved in creating the spreadsheet(s) required, gathering the data, and then uploading, with the benefits. If the current data is correct, then it wouldn't hurt if you didn't take the time to upload the data.

However, keep in mind that if you're going to upload the data, then that will help with verification. So, since you've taken ownership of those listings, there's a better chance that you may rank better and show up more often in the search results because those are verified listings. This goes for Bing as well as Google.

So, yes, I do believe it is "worth it" to take the time to verify the listings and upload the data (and take ownership of those listings).

No, Google does not penalize you for having content that requires registration in order to view. As long as you give Googlebot full access to the content so that they can crawl it properly, it won't be an issue. There are plenty of sites doing this successfully, and they don't have any problems.

Rasmus,

Google has been doing this (changing your title tag) for a while now. Google doesn't normally just "guess" your brand name or website name, they usually get it from somewhere. I would try to find out where they are getting it from and see if you can change it there. As Andy suggests, if it's your WordPress blog, then there is a chance that they're taking it from your blog's title, and you should be able to change it.