We spoke with Matthew Mengerink, VP and GM of eBay’s x.commerce, which offers merchants an e-commerce platform using the “fabric of eBay” and its various products to essentially be the ultimate set of APIs and tools for e-commerce (though it also applies to getting people into brick and mortars with mobile apps).

Mengerink and his colleagues are spending a few days in Vegas at the Imagine conference, getting to know the developers that are helping them build their ecosystem (which is growing quite well, by the way).

With x.commerce, Mengerink says, there have been five to six thousand Magento extensions and seven thousand PayPal extensions created by developers in the past year. They’re seeing something like 300 a week for PayPal. There were two thousand Magento extensions installed in the first quarter alone.

eBay/x.commerce announced some new partnerships at Imagine, which should fuel the growth of the ecosystem even more, and add to eBay’s own “fabric” with their own services for merchants o take advantage of. New partnerships are with: Avalara, e-Dialog Express, Fanplayr, Kabbage, Lexity, M2E Pro and TheFind, which have each developed new capabilities based on eBay’s Magento platform. The goal, according to Mengerink, is to keep costs down for merchants, and eliminating the complexities of using multiple solutions. He also emphasizes the ability for merchants to easily switch integrations on and off as they see fit. Because of this ease, he says, merchants can experiment more across different services.

Avalara is offering AvaTax through x.commerce for tax services for merchants, including tax calculation, exemption certificate management and returns processing.

e-Dialog Express is giving Magento merchants email marketing tools, such as an email editor and tools for tracking email opens, clicks, pageviews and social sharing.

Fanplayr offers Coupon & Offer Gamification for Magento merchants to “harness the marketing and sales capabilities of ‘Smart & Targeted’ coupons”.

Kabbage provides funding for online sellers, and uses Magento to streamline the application and payment process for merchants, using PayPal via the X.commerce platform. Kabbage disburses loans to merchants via PayPal Payments, and uses PayPal’s PreApproval API to establish automatic repayment of loans, as x.commerce explains.

Lexity actually offers a search engine marketing platform for Magento merchants, which implements AdWords campaigns. It automatically manages and optimizes keyword bidding.

M2E Pro’s extension integrates Magento and eBay platforms for listings management, synced stock level, imported eBay transactions and orders, and feedback.

Finally, TheFind provides a shopping search engine, indexing over 450 million products from 500,000 online stores for comparison shopping. With the Magento integration, merchants can add it to their own stores.

At the conference, developers are showing off their stuff at bar camps, and getting together at mixers, which Mengerink cites as his favorite part of the event, because it “fosters the ecosystem”.

According to Mengerink, eBay has x.commerce set up so that anytime the company makes a new acquisition, it can quickly be integrated into x.commerce, to add to the fabric. Between acquisitions and partnerships, they’re going to give merchants a lot more reasons to tap into x.commerce.