(Update: EBay has gotten back to us, and says Meebome is not welcome there. Our update is here)

Meebo, the start-up that lets you instant message online across different platforms (Google, MSN, Yahoo, AOL, etc), has created a cool little widget that lets you chat with anyone directly from your homepage — and threatens to shake things up at places like eBay.

It is called Meebome, and the details are here. We’ve embedded it on our homepage (on the right hand column of SiliconBeat) and also here on this post, so that you can we what it looks like. You have to be registered at Meebo to be able to chat. To our knowledge, there is no other feature that lets you chat to various people — individually, via one-to-one conversations — from pretty much any Web page. There is Gabbly, but that is group chat, and it produces lots of noise because everyone can see what you are writing to everyone else.

That homepage where you put Meebome can be wherever, from your MySpace account, to your blog, to your listing page at eBay. We think this is significant for a number of reasons. First, this is a very fun feature for regular bloggers, the ones with only four or five people reading their blog at any given time of the day. It lets people chat on the various pages that make up their identity — allowing one chat box at their workplace page, for example, and another on their Burning Man blog. The blogger can decide to reveal whether they are present to chat or not, and the reader on the page can do the same — just like in normal chat.

Second, and more profoundly for ecommerce, it is a simple feature that pushes forward IM-presence on the Web for merchants. Let’s see whether eBay permits it on their site and allows chat directly between buyers and sellers. There are early signs that eBay may be bugged by this, but it is too early to tell.

We ran this by eBay spokesperson Hani Durzy, and he said eBay’s policies do not allow links to IM clients. But we spoke to Hani yesterday, when the Meebome feature still hadn’t been released, and so he reserved judgment until he sees it. “What we’re not allowing is links to live chat systems,” he said. “Might we revaluate? Sure, we’re constantly monitoring what our community wants to do.” We’ll report back when we hear from Hani today.

Seth Sternberg, chief executive of Meebo, meanwhile, says he thinks eBay will like it. That’s because eBay’s chief concern is to avoid conversations being taken off the eBay platform and into the grey market, he said. Meebome keeps conversations directly on eBay, since the widget is embedded there. “I’d therefore think that Meebome would discourage grey market transactions as opposed to email, etc, as it keeps buyers in eBay, on the listings page. I seriously think they’ll love it!” (Seth is openly testing eBay at his page)

Well, we’ll see, because eBay has been squeamish about allowing free chat. It has carefully allowed testing of the SkypeMe button on the listing pages in certain categories. Those 14 categories include large categories such as vehicles, and niche categories such as “Lost in Space” memorabilia. “We know for some things, the ability to communicate through voice chat will help us sell certain items and get higher average prices,” Hani said. These areas include highly priced items, such as jewelry, or technically complex items, including routers — where it helps to allow questions between buyers and sellers. eBay’s policies differ by nation, too. In eBay China, 30 percent of all pages have chat, he said.

EBay also allows one link on a listing to an email address, but bottom line is you just haven’t seen an open embrace of chat between buyers and sellers (despite eBay’s acquisition of Skype quite some time ago).

Also, Seth told us yesterday that WordPress, the popular blog platform has made Meebome its third standard widget for WordPress.com, the hosted “closed” version of WordPress. The other two are Delicious and Flickr.