Pashmina is absolutely true in the fact that not anyone can give you an accurate limit. Also, pointing out the 30 anchor links that she is specifying leads me to believe it's based on a great article that Randfish wrote.
This is the link to the article here: Testing the Value of Anchor Text Optimized Internal Links
You will notice that he replies to a commenter with the following questions:
"Very interesting Rand. I've always wanted to test the effects of internal anchor texts.
You stated that excessive internal anchor text linking can trip an automated penalty, what do you consider an excessive amount? Thanks for opening our eyes to this."
Rand's answer was based on his observation as the following:
"I honestly can't say where the limit lies, but in both cases I observed, there were in excess of 30 links sitewide that were clearly anchor text optimized to push rankings."
Although this info seems to be valuable information, it may be outdated and hold less value to the current time.