If I held a raffle for a prize, where site owners could get an entry by linking to my site with certain anchor text, then emailing me to let me know about the link, is there any risk of being penalized in search engines?
I don't know if there is any penalty for it, but I think the advantage may be limited. Once your contest is over, most of the links will be taken down. Old links are worth way more than new links, so the advantages would be minimal I would think, that is unless you are just looking to get indexed.
John Chow did this a while back to get linked for "Make Money Online," and it worked very well initially, but Google found out and took him out of the SERPs.