Sigh. Zipcar, short-term rental car service that has occasionally made my life a lot easier, just got swallowed by Avis:

Zipcar Inc. has been growing as more people in urban areas forgo owning a car and instead tap car-sharing and hourly rental services when they need a vehicle. The company’s third-quarter sales grew 15% to $78.2 million while its membership (renters) grew 18% to more than 767,000. Zipcar earned $4.3 million in the three-month period and has said it expected 2012 to be the first full year for which it posts a profit.

Avis Budget, the nation’s third-largest car rental company -- after Enterprise Holdings and Hertz -- will pay $12.25 a share in cash for Zipcar, a 49% premium over the stock's closing price Monday.

Avis believes it can whittle $50 million to $70 million of expenses out of the combined operations of the companies by eliminating duplication of functions such as the cost of maintaining Zipcar as a publicly traded company.

Just once I'd like to see a cool, niche company grow to a sustainable size without being acquired by a huge corporation.