Being a big fan of definitions and the history behind words, I recently pondered the exact definition and qualifications to be deemed a "boutique store".
1. a small shop or a small specialty department within a larger store, especially one that sells fashionable clothes and accessories or a special selection of other merchandise.
2. any small, exclusive business offering customized service: Our advertising is handled by a new Madison Avenue boutique.
3. Informal . a small business, department, etc., specializing in one aspect of a larger industry: one of Wall Street's leading research boutiques.
Origin and history - boutique "fashion shop," 1953, earlier "small shop of any sort" (1767), from Fr. boutique. French for "shop".
More on it's history and origin Wikipedia-
The term entered into everyday English use in the late 1960s when, for a brief period, London was the centre of the fashion trade. Carnaby Street and the Kings Road were the focus of much media attention as home to the most fashionable boutiques of the era. Now the East of London has been regenerated and more Boutiques pop up in fashionable areas, such as Tower Bridge Road.
In late 1990s some European retail traders developed the idea of tailoring a shop towards a lifestyle theme, in the form of "concept stores", which specialised in cross-selling without using separate departments. One of the first concept stores was 10 Corso Como in Milan, Italy followed by Colette in Paris and Quartier 206 in Berlin. Several well-known American chains such as Urban Outfitters, D-A-S-H, and The Gap, Australian chain Billabong and, though less common, Lord & Taylor adapted to the concept store trend after 2000.
