How we got here: Web App Stores
The recent sudden popularity in web "app stores" is taking off with a rate normally associated with fads, but in some respects is actually to be expected. Still, it bears an interesting similarity with one of the oldest types of websites that the average consumer has seen: directories.
Back in ye olden days (1996), lots of tech savvy individuals were creating websites...only one problem. Discoverability! Now that they've launched www.awesomesauce.com, how do they tell people about it? They could either rely on word of mouth, or they could submit it to...Yahoo!, which kept lists of worthy websites in directories.
It wasn't long before websites running these directories realized they could write a program that browsed the websites that were listed on their directory and archive the discovered text into a database, and then expose this database to the public via a convenient form in their handy dandy Internet Browser (alternatively, you could "submit" your website to search engine to tell them to index it...you still can, too).
However, most of the search engines weren't very...good. If you searched Excite and Lycos didn't find what you were looking for, you'd try another search engine (WebCrawler?). Still didn't find what you were looking for? Keep looking! Maybe Altavista has it!
The tech folks realized this, too, and came up with a somewhat reactionary response: make a search engine that searched other search engines. Metacrawler? Hell yeah. Your one query would show you results from two, three, or more other search engines. Even now, Metacrawler searches Google, Yahoo!, Bing, and Ask (which, for the record, appears to be the same as WebCrawler now).
Then along came Google. Google had three main allures: it was simple (no bloated "search portal"), it had great (and fast!) search algorithms, and indexed damn near everything (1998-2000). Lots of people were contributing content to the web, creating their own sites on Tripod.com, GeoCities, and Angelfire. The amount of content search engines were indexing continued to increase. Unique page counts increase from thousands to millions to billions (Google is purportedly around 20 billion pages now, see http://www.worldwidewebsize.com/).
Innovation slows a bit (well, a lot) when the dot com bubble pops, when companies realize that simply having a website doesn't guarantee multi-million dollar successes (shocking!). While people are still playing with JavaScript and making pretty animated snowflakes tumble down the tops of their GeoCities pages, Google does something unprecedented: it releases Gmail on April 1, 2004, creating one of the first major web applications (what we now call "Rich Internet Applications") the world had ever seen, and launched it into the spotlight by offering an unprecedented amount of space in the inbox: 1 gigabyte! Other web-based email services existed, like MSN Hotmail (with 2 megabytes for email storage), and Yahoo! Mail (with 25 megabytes of email storage on the premium plan, $30/yr), but these suffered from various issues from security to slowness to being downright ugly.
Gmail, besides revitalizing the webmail industry, showed us all two things: 1) Javascript can be used to be, well, useful, and 2) XmlHTTPRequest is incredibly useful (and iframes, bleh). This begins the trend of taking web applications seriously as a replacement for certain desktop applications.
Fast forward a few years -- there are now many many Web 2.0 apps and/or RIA apps. So many, in fact, that there is a veritable glut of apps. We have a new discoverability problem, but not because we can't find the apps we need, but because we can find too many apps that could fulfill our needs. How do we deal with hundreds of todo list apps, dozens of task-management apps, scores of invoicing apps, etc etc?
Well, there are a few things. SEO (and search), word of mouth, getting featured on news sites, and awards. But those are all so...qualitative. None of those things means a product is necessarily even what you're looking for, except for getting covered in a story perhaps, but even that is only the opinion of one person. What if you want reviews from lots of people, and not just journalists? Or reviews of all sites, not just sites popular enough to get noticed by the media? And that's why we'll be seeing an increase in web app stores -- they're low barrier to entry, help people learn about online tools from other people, and are more structured. People will be able to find what they're looking for without having to figure out the best combination of search keywords. This is definitely a good thing, provided that superior web products get the attention they deserve and incumbency means nothing. Looking forward to what the web has to offer, again!