I personally am happy to build 100,000 links to my site in 1 day, why? Because external links will not hurt mysite.
What may happen is that 99.9% of them linking pages will end up in Google's supplementary index rendering those links worthless, and for the other 0.1% Google may decide to devalue them links as they look un-natural.
I'm not saying that Google doesn't like sudden a spike in links, which is usually an indication of content going viral, but your links do not have any diversity.
Consider the following:
Followed links
No followed links
Links from different root domains
Blog post
Blog comments
Press release
Forum posts
Signature links
Anchor text
Page rank
Any kind of spike in links should include this kind of diversity.
If you're just going to build links that are from forum posts, followed only, no page rank, and same anchor text, then expects those links to be devalued.
Have you heard about the recent penalty that was given to JCPeeny? This was APPARENTLY due to them buying links, but be sure there are other factors that have not been revealed. Google needs proof to do such a thing, or face a court case that they will lose.
There is nothing stopping a competitor to build links to your site so that you would get banned, so Google can't use external links to penalize you.
A reason to build links to your links is to get them indexed. A link that has no ACTUAL page rank is worthless. If you decide to just ping your links, then it MAY only get indexed for a short time due to there still being no pagerank, and by page rank i mean real page rank, not toolbar. even 0.02 worth of pagerank will get indexed.