i wrote a parser for NBA games, get the data straight from yahoo. Using Python and BeautifulSoup, piece of cake. I would think MLB could work the same.
Yeah, HTML scraping ESPN.com is not very hard. I did it for college basketball once in a strange sort of database that attempted to predict March Madness brackets. It worked really well for teams that had encountered each other during the season... except only 2 or 3 pairs of teams had ever played each other during the regular season. Works much better on NBA and NFL games, where there are far fewer teams, they see each other more often, and the rosters are a little more static.
I've seen a few people respond with this "you can just html scrape that." Sure you can HTML-scrape for the information, but the topic of this "Ask HN" is about what APIs you would like to see. Maybe he already HTML-scrapes ESPN.com, but would prefer that there was an official API for it, no?