Truth is, this is nothing new, people have been impersonating Matt Cutts since the GoogleGuy days. I've seen many comments here from "Matt Cutts" that were indeed not from Matt Cutts, I've seen people claim Matt emailed them when he did not.
With Matt Cutts on leave, it makes it even harder to believe that he is responding to SEO questions on blogs or email.
So when Paul Botham posted in Google Webmaster Help forums that Matt's blog was hacked and he was emailing back and forth about penalties with Cutts, it had to be a lie.
One, the blog that he is referencing is mattcuttsblog.com which is not owned by Matt Cutts himself.
Two, Matt is on vacation and is staying out of search quality topics while he is gone.
Three, Matt would only email you from an @google.com address, not a gmail address or something else.
Google's Eric Kuan came in to clarify in the thread:
Just wanted to confirm that mattcuttsblog.com is not Matt's official blog as nidya and others have pointed out. And unfortunately, that wasn't Matt responding to you on that email thread.
In the future, if someone from Google does contact you, it will most likely be through an @google.com email address. Feel free to post in the forums again if you do encounter any suspicious emails.
I'd also be wary of anyone who promises you of a guaranteed ranking boost of any kind. In fact, any type of guarantee about ranking or a boost in ranking whether it be from Google or another company should send up a red flag. This article has some more advice that you might find helpful: https://support.google.com/webmasters/answer/35291.
Just a final note about links. Low quality links can negatively affect your site, and if you do find any, I would try to get them removed as soon as possible. If you're unable to contact the webmaster to remove the links, you can use the disavow tool in Webmaster Tools.
So don't fall for fake Matt Cutts impersonators.
Forum discussion at Google Webmaster Help.