It's definetly wise not to create tons of backlinks in a short time. Google can sandbox you for this backlink method. The best way to create backlinks is placing backlinks by hand and not to many in a short time.

I would say that the aceptable number of links that could be built per day would be 150-200 but it all depends what kind of links you are building. Of course its not good building so many links every day but maybe 2-3 days a week is ok.

Your link building friend is right you shouldn't build too many links per day. The best thing to do is to build different kind of links, like couple of blog links, forum links and do a bit of link exchange with other web sites to and you will be fine.

I have built about 100 links per day and it doesn't seem to be a problem. Probably if you build like 400 per day Google will start looking at you differently.

On of the main concerns is the age of the site, a brand new site suddenly getting thousand of links will be regarded as suspicious. An older site does not really have to worry about this but you really do not want thousands of links a week, I stick with 100 a week when I decide to work on backlinks.

I definitely agree that we like quality links rather than quantity. When I was starting as a link builder I just do a lot of blog commenting, but then I realize I'm just wasting may time on that. I wasn't seeing good results. So, what I did is that I read articles to give me more insight and understand what to do. Now, I'm only focusing on quality backlinks, and yes I'm seeing results coz' my website's ranking is improving. 

I believe its the quality of the link that is more important than quantity. I think its better to have more reputable and trust worthy websites sending traffic to your site rather than spam links that are easy to obtain.  

I have also heard that you cannot be penalized by too many or bad backlinks. If you could be penalized, wouldn't your competitors simply spam sites and create poor backlinks to your website to knock you out of the google natural seaches? You cannot control who links to your website, so I believe you cannot be punished.

Thanks ... 

You absolutely DO NOT want to dump a thousand links out there at one time. Therefore, don't use automatic submission software. Best to do it manually, maybe 25 or so per day and diversify - blog posts, directories, social bookmarking. Might want to throw a couple of nofollows in there occasionally to make it look natural. Be sure to ping your link with pingomatic or similar service if your link is posted immediately to get it indexed faster.