Twitter enlisted Citysearch as the first user of its Sign-Up API, which helps new users create Twitter accounts from other people’s web sites. Citysearch gets a sprinkle of social media goodness from the arrangement, fostering real-time interaction between consumers and companies, while Twitter — which has a notoriously inscrutable new user experience — gets someone else to handle customer acquisition of smaller brands as it prepares to offer corporate accounts. Citysearch says it has direct relationships with some 200,000 local merchants, and it wants to build a multi-service social media directory for small businesses.

Aaron Patzer launched Mint.com as a user-friendly alternative to Quicken and other personal-finance software out there. Little did he know that just two years later, Intuit, which makes Quicken, would fork over $170 million for his website. Patzer, an Inc.com 30 Under 30 alum, is also featured in the new book, Upstarts! How GenY Entrepreneurs Are Rocking the World of Business (www.upstartsrock.com), by Inc. contributing editor Donna Fenn. She recently caught up with Patzer to discuss the big sale, what his new role with the company will be, and how he’s planning to change the future of transportation.